UNI VE RS ITY O F CA LI FO RN I A

DE PA RTME NT O F MI N I N G A ND META L LURGY

A SSAYI NG L A BO RATO RY

HRI Y S . B . C S T

De a n

LA BO RAT O RY I NST RUC T IO NS FO R

IRE A SSAYS F GO L D F O ,

E R A ND L E D S ILV , A

MI NI NG 1 07 a - b

M RLEY WA LT E R S . O

A s sistan t Pr ofe s s o r o f Me t al l ur gy

UN IVE RS I TY O F C ALI FO RN IA PRE S S BE R $ E LEY

1 9 1 3

PREFACE

These instruction sheets have been prepared in this form to take the place of mimeograph copies which were formerly used by students electing the course in fire assaying at t h eUniversity

n of California . These notes are co cise directions for the carry

t o i ing out of cer ain lab ratory work , and in no w se cover the ground of the lectures which supplement the instruction in the b la oratory . The purpose of the course is not to teach merely practical

s fire as aying, but also to familiarize the student with metal l u r g ica l principles which underlie smelting operations on the l a rge scale ; and in the lectures as much emphasis is placed on the underlying metallurgical principles as on the practical details of fire assaying .

' n -five e The laboratory work is divided i to twenty assignm nts , thirteen‘ of which are intended to cover the work of the first

- t half year, and the remaining elve , the work of the second half

e n s n y ar . In addition to the twelve assig ment of the seco d half

as n year, there will be given , time permits , assig ments relating n an d to the fire assays of mercury , tin , cobalt , and antimo y , the

b ash . determination of car on , sulphur , and in coal and coke

TABLE OF C ONTENTS

CHA P TE R I P RE L IMINARY W OR$

1 .

2 P a i e in Cu el l a n . r ct c p tio

P a in l a n d l e 3. rt g Go d Si v r 4 e A ssa L ea u l l n . Fir y of d B io

CHA P TE R I I

S CORIF ICATION A S S AYS

S c or ifi c a t ion in Gen e ral S c or ifi ca t ion of Sil v e r Or es $ u a rt z - Gol d Or es con t a in in g l ess th a n on e -h a l f P y rit e $ u a rtz - Gol d Or es con t a in in g more th a n on e -h a l f P y rit e S c orific at ion A s s a y of Sa mpl es High in Copp er

n l f ul S c or ifi c at ion A ssa y of Or es a d P rodu ct s Fu sib e with Di fic ty . Gen era l P ra ctic e

CHA P T E R I I I

CRU CIBL E A S S AYS

Det e rmin a tion of Gol d a n d S il v er in L ith a rge : of t h e Redu cin g

P e s C a a l A ] an d l u a n d A ss a l u es ow r of h rco , rgo , F o r, y of F x $ u a rt z Or e s $ Nitre A ss ay for Or es con t ain in g Mod era t e A mou n t s of P y rit e Nitre A s sa y for Ore s con t a in in g L a rg e A mou n ts of P y rit e Ro a stin g Method for Or es con t a in in g L a rge A mou n ts of P y rit e $ ” A ssa y of Sul phide Or es b y Na il Me thod A ss a y of T a il in g s

CHA P TE R I V

BUL L I ON A S S AYS

A s sa y of Gol d Bu l l ion Fir e A ss a y of Sil v e r B u l l ion

CHA P T E R V

MIS CE L L ANE OUS W OR$

u n a R a i s Ma n u l s F r c e ep r . ki g C p e

Mel in Re n in a n d a l n l a n d il e u l li n t g, fi g, S mp i g of Go d S v r B o Comp a ris o n of Method s for A s sa y of Copp er -b ea rin g Ma t erial s

P a i e in a l n P a n n in a n d A a l a a in r ct c S mp i g, g , m g m t g Fire A ssa y of L ea d Ores

[5] THE NOTE—BOO$

s e a i n ea a n d a u a e n e - a in is u s a s u n ot y , t cc r t ot t k g of j t m ch , if $ S t m t c e a n e t h e s u en fi r e a ss a in a n t h e a u a l a l mor , import c to t d t of y g th ct det i s

h e s el Ca e u l n e - a n in l es l se se a n a n d of t work it f . r f ot t ki g vo v c o ob rv tio

i n A n u i a l s l i n en a . e e e e u u a s a e en h co c tr t o m r m r c r t , w tho t t t m t of t e

n i i n s n in t h e e i en is n ot w a n W l e e e . a a u a co d t o gov r g xp r m t , t d ith p rtic r num erica l r esu l t shou l d b e giv en a l l t h e e ss en tia l fa cts con c ern in g t h e e e i en a s e e n e b se a i n ea in a n d u xp r m t , d t rmi d y ob rv t o , r d g tho ght

s e a n d n ea n e ss a r e ess en ial a a e is i s a en n ee Sy t m t t ch r ct r t c of good gi r, s ia l l a in in e n in e e s e u ies e n a e h im in l s e p e c y m g g r, who d t oft t k to p a c e

. h a i n d - s r t h u l e e s a e a e e e . wh r rd h p , dirt , di ord r r

Y ou sh u l a e u n e - n ot n l n t h e l e u e u t o d t k y o r ot book o y i to ct r room, b l W n u s a n i in to t h e fu rn a c e room a s w e l . rite dow y o r ob erv tio s wh l e

h $ u n e - l a n a r s in u e . ee e u i in t ey e fr e h y o r m mory p y o r ot book c , y o r wr t g

l e i l e a n d u a n s n ea . g b , y o r dr wi g t

P l a n a n ies a r e e e e a n d e s u l b e a n rop er y t k e c rbo cop xp ct d, th y ho d h d ed in n l a e a n on e ee a e t h e e e i en h a s een e e ot t r th w k ft r xp r m t b p rform d .

[ 6] REGULATIONS COVERING W OR$ IN THE ASSAYING LABORATORY

d Before commencing work , each student should be supplie with the folowing articles

’ 1 M l o F ir A s a in a n u a e s . . Copy of Fulton s f y g

2 . - Capsule box containing six porcelain capsules , three

$ -flasks unglazed capsules , three ennedy parting , three

an . test tubes , needle d mag nifier

r - Laborato y folder with centimeter ruled paper , ar a ranged for c rbon copy .

k ' l H i HH lead pencil .

mS et of Becker ( or equivalent ) weights from 1 gram to

1 / /1 0 milli gram .

- Pair of bone tipped pincers .

s- Pair of steel pincer .

Pair of bead pliers .

- Blow pipe . 1 0 . Laboratory suit .

E ach student should report promptly for work at the a p h pointed hour , and s ould stay the full laboratory period , unless excused .

‘ ’ All fires should be drawn by o clock .

All apparatus should be left in its proper place and in order .

[ 7] CHA P TE R I

PRE L IMI N A RY WOR$

A SSI GNME NT 1 WEIGHING

In this assign ment you are exp ected t o become thoroughly

r n a d u st men t ~ u se familiar with the const uctio , j , , and care of an assay balance . Read carefully all the references given at the end of this assign ment h An assay balance is similar to a chemical balance , except t at

n of l imit in the movi g parts are made lighter, and instead g the 1 0 1 0 . sensibility to . mg . it is made to weigh accurately to . mg With th e balan ce you use this is don e entirely by the method of

efle n b e e d ctio s . Later on you will given a balance with a rid r .

e n n Calculat the se sibility of the balance assig ed to use , as

: follows After a couple of oscillations take readings , first on one — side and then on the oth er for example :

P A N s E MPTY

2 05 ) .

-03 t t ft Res in g p oin , le

Repeat the re adi n gs un til un iform results are obtained

s n ot n s t h e the resting point do agree , i crea e number of readings on on e a side . After a little practice , two readings on side and

n ffi o e on the other will su ce . e I n this assign men t record all readings in your notes . Aft r

e n n eces you have become skillful in r ading , recordi g will not be

. n a sary . In taki g re dings do not let the needle vibrate more than a total of five divisions . [8 ] e Now place your mg . weight on the l ft pan , allow needle — e an d e t h e - f o r to swi n g as b fore , det rmine new resting point example

M W E GH ON L E F P A N G. I T T

7 1 5 3 33 2 )

5 2 4 2 n d r t t h t es in g p oin , rig

03 l s t r t t f t es in g p oin , le 5 2 7 D iff eren c e

The difference between the two resting points is the numb er l of division s on the ivory index through which é mg . has caused

n fl the eedle to be de ected . The sens ibility of a balance may be defined as the deflection

1 m Or s in n t h e caused by g ; , expres ed a other way , sensibility is the weight in hundredths of a milligram which will cause t h e

e e on n ne dle to be defl cted e division on the i dex .

n or In the above example , the sensibility is divisio s . 095 . mg .

ou e n e As y can readily r ad to tenths of a division , the bala c 1 0 . will be sensible to . mg Were the beam perfectly rigid , this sen sibility would hold for much greate r loads than are usually

$ s weighed on an a say balance, but for a load of even grm .

e 1 there is a perceptible change . To t st this , place a load of gram on each pan of the balan ce and determi n e the sensibility as you did wh en the load was zero . Compare results .

defl ect ion - You are now ready to weigh by the method . Obtain a number of pieces of gold or silver weighing from 1 to 1 0 m e

n Weigh each separately and the all together . Add up the separate weights and compare with the total weight . Repeat until your results are consistent .

[9 ] u ll an d c om l et e u Make a f p record of yo r observations .

Before leaving the balance see that the beam is . lowered and the case closed . The foregoing method of weighing is specially adapted to

n in the poorer grades of bala ces use . When a rider attachment $ ” - d eflect ion is available , the rider method may be used , the

n 2 m m rider taki g the place of the g . and s aller weights . This method is the one ordinarily used in assay work . With an exceedingly sensible and well - constructed balance the method

' $ ” ’ of n o deflect ion s (see Fulton s Ma n u al of A ssayin g ) may be used .

n n Make a drawi g of your bala ce shelf , showing the method used to secure a firm foundation : give dimensions of foundation

S . supports , width of helf, etc

RE FE RE NCE S

l /l 42—52 u n : Ma n u a l o A ssa . . F to f y g , pp

A n s a in I 2 — n 1 2 a : A s a . 7 38 a d 7 ro y g , p rt , pp

n it i h c n i - T e : a t a t ve emi a A a l s 3 33. u l s . horp $ C y , pp

Ca a l u es es i i e Of t h e a l a n e s a e b e e T r o emn er t og d cr pt v b c m d y B ck r, ,

in s i T n a n $ l l A s d e e . worth , Sm th homp o , r

A SSI GNME NT 2

PRACTICE IN CUPELLATION

A e e ffl . Place half a doz n dry cup ls in the mu e and build a

fire in the usual manner . As coke is used for fuel , it is necessary to have a good coal fire start ed before adding the coke . Let the

ffl e mu e heat up until a bright red is reached , th n arrange the

n dampers so that th e heat remains u iform . Before cupelling ,

ffle see that the fire is solid around the mu . u 1 5 Now obtain six lead b ttons , weighing approximately

n : grams each . Cupel in sets of two each in the following ma ner Bring two of the cupels forward say withi n two inches of the

ffl bfit t on m . front of the u e Place a lead in each , using the cupel

[1 0] th e s n tongs , then shove cupel back i to the hotter part of the

ffl $ ffl n h e a . t mu e . Close the mu e door for few mi utes When

$ as o buttons have melted and cupellation has commenced , sh wn

n s . O en by the fume of litharge , p the door and arra ge the dampers so that the fumes are drawn slowly off through the rear of the

ffl n s mu e . Try to keep the temperature constant , i crea ing it only

. when the lead has . almost disappeared The heat is too low

s an d when the fume become heavy dark , and a scum forms around the edge of the molten Th e h eat is too high when ‘ the fumes of litharge rise rapidly t othe t op Of th e muffle and ” ea $ u ' the l ead appear s to be boiling . The h t is j st right when r ra crystal s of litharge fo m in the cupel . P ctice will enable you

n s to fix upon the proper co dition . Cupel the remaining four and as many more as you h ave time for during the period .

' l c Make a f u ll an d comp et e re ord of your observations . Study carefully the following references

RE FE RE NCE S

’ — n : Ma n u a l O A ssa in . 2 1 4 2 2 3 . Brow f y g , pp

n in 1 8 - 1 42 u a : A ssa . 3 . F rm y g , pp — 4 e a n $ e l : A ssa in . 1 1 0 1 2 . Bod m r y g , pp ’ — R n 1 09 1 1 5 . h ea d $ S exto : pp .

n B . Roll out a silver coin to the thickness of an ordi ary

n O a . visiting card . A neal the coin repeatedly during the per tion

$

Clean with sandpaper . Now weigh out on your bead balance six — a s n 25 30 . as ays of this coin , three weighi g mgs e ch , and three — 90 1 00 . a weighing mgs . each . Weigh each bead accurately Wr p 1 5 each as say in grams of sheet lead , weighed approximately on the pulp balance . Arrange these six assays in sets of two each ,

n 2 5— 0 90 so that each set will con tain o e 3 mg . assay and one $ ” 1 00 a A ss . mg . a y Cupel one set at a time , as in , only using

‘ more care on account of th e resulti n g silver bead . Try to s feather the cupels and at the same time brighten th e bead .

[1 1 ] Remove the be ads from the cupels and clean thoroughly by

‘ e brushing . Place th m in their respective capsules , and take to

the balance room . Weigh , and report in this form

S ilve r A C B fi m r k a N . a a ss y o oin W t . e d neness Re s 1 88 0 W el l fea thered ; brig hten e d a t e ea prop r h t .

Th e as term silver fineness , used above , refers to the number 1 000 of parts of silver found in parts of the coin .

an d Compare the results , note the average percentage silver 25— 0 h —1 3 . 90 00 s t e . s losse for the mg assays and for mg a says ,

taking into account , of course , the known fineness of the silver

coin used . Dissolve a piece of coin silver in nitric acid and test with ammonium hydroxid for copper ; also test a well - brightened bead

n n ? in the same ma er . What deductions do you make

C . s Obtain from the storeroom , six lead buttons packet ,

n s e havi g , re pectiv ly , the following compositions

1 n a d . . Lead silver

an d . Lead , silver gold

an d w Lead , silver antimony . Lead , silver and copper . ‘ 9 Lead , silver and tin .

3 3 n 5 Lead , silver and iro .

i n n e e . s m Cupel s ts of two ach E deavor, in each ca e , to ake

e n . e a p rfect cupellatio Observe , carefully , in each case , the h at , time and manner Of brightening ; observe the formation of any

s r scoria , its color , etc . ; note , in each ca e , the colo and general appearance of the cupel after brightening .

n l t Make a fu ll a d comp e e report .

[ 1 2 ] A SSI GNME N T 3

PARTING GOLD AND S ILVER To be a successful assayer one must be able to part correctly

n and rapidly . Nicety of ma ipulation is required , and the only

DO a way to acquire this is to practice conscientiously . not t ke ’ n anythi g for granted . There are three steps in an assayer s

r : 1 work whe e he must be sure , viz ( ) That the sample is what

it represents ; ( 2 ) that nothing but gold is weighed as such ;

( 3) that the weighing is done accurately . With these points

looked to carefully , the rest will be comparatively easy . Perform carefully t he following experiments / W eiglit ou t six pieces of gold foil on your bea d balan ce to 01 m n . 5 . . g ; each piece should co tain about mgs Alloy the pieces 1 2 3 4 5 8 of gold with , , , , , and times their weight of silver ,

S respectively . Weigh the ilver also on your bead balance , to 1 0 . mg . only . o 1 To alloy, wrap the g ld and silver in about gram of sheet

uffl lead and cupel in the m e , taking care to have the cupel

n o ffl a d h t . smooth , dry The mu e should be slightly hotter than

n a . a for ordi ry cupell tion . After alloying remove the bead from

b ~ ¥ mean s the cupel y of the bead plyers , brush thoroughly , and

h . e place in t e porcelain capsule used for parting . Tr at each of fl the five beads thus and remove to the parting room . Now atten

c n . ea h bead , usi g the small blowpipe , hammer and anvil Return

n them to their respective capsules , which should the be filled w with hot , eak parting acid ; heat slow ly on the hot plate , and

a t when all action has ceased , repl ce the spent acid wi h strong acid and heat for three minutes at boiling point . Then remove

Off an d s from the plate , pour the acid , wa h three times with distilled water ( preferably warm ) . Dry over the hot plate , then fl anneal by heating to redness over the Bunsen ame . Cool and weigh . Report results in this form :

G t a k S v at W t of a t G m a r k Wt . old en il er R io . P r ed old Re s 1 1 n a i to Not a ct ed u po b y c d . What do your experiments determine ?

[ 1 3] niin u t el Describe y the action of the acid on the several beads . — NOTE Flatten all doré beads unless they are known to con tain more than eight parts of silver

RE FE RE NCE S

n : Ma n u a l o A ssa in 224—239 Brow f y g , pp . .

u a n M n — l . A s a in 45 46 : a u a o s . 1 1 F rm f y g , pp . _ e a n $ e l — 0 A s a in _ 1 98 20 : s . Bod m r y g , pp .

u l n : Ma n u a l o A ssa m/ 1 0 —1 1 0 F to f y g , pp . 7 .

A SSI GNME NT 4 FIRE ASSAY OF LEAD BULLION

off A T sam es Chip or saw four . . fl from the bullion given ’ a u you , and ssay according to the directions given in F lton s

Ma l o A sa in n u a f s y g . Report both gold and S ilver values I n this form

Per ton

To get correct results in this as signment the cupellation must

n s be do e perfectly , so in a measure this assignment will te t your

ability to cupel .

n A T Explai the term . .

RE FE RE NCE S

— u a n : Ma n u a l o A ssa in . 1 4 1 7 a n d 2 72 2 75 . F rm f y g , pp

[ 1 4] CHA PTE R II

S CORI E I OA T I ON ASSA YS

A SSI GNME N T 5 S CORIFICATION IN GENERAL

I n this ass ignment you are expected to get a general idea of the scor ificat ion process as far as can be done by reading A brief outline Of the work in scor ifi cat ion is given below

1 or i tio o . S fica n assa y f sil ver or es

( a ) Silver - lead ores

Those containing no lead , but quartz , metallic silver

and silver compounds .

A general charge for ores of the above clas s is :

r e A T O $40 . . — Gra n ul a te d l ea d 30 35 gra m s Bora x gl a s s gra m

in r ifi r Use . s c o e s

r This cha ge , with slight modifications , will treat any silver ore ;

'

‘ o n 50 r it e t h e if the ore c ntai s more than per cent of py , lead

n e s 45 may be i cr a ed up to grams . And if much lime , zinc or

a antimony is present , the borax glass must be incre sed up to as much as three grams in exceptional cases . Where the sample is rich and at the same time homogeneous the weight of the A T sample taken may be decreased to .

2 S cor i ca tion as sa o r ich old or es . fi y f g

seor ificat ion As will be noticed from your reading , the ” assay is primarily adapted for silver ores and rich g old ores . for evident reasons . To get the required amount of sample for d a me ium or poor gold ore , it becomes necessary to make several

r fi i n s s co i cat o and then scorify the resulting buttons together , or cupel separately and part together .

[1 5] a e n n r — ( ) $ uartz gold or s co sisti g la gely of quartz . The charge given for silver ores ca n be used equally well for quartz

e n n in s 50 n in gold or s co tai g les than per ce t pyrite , though most

e is e e A T n n cas s it bett r to take mor than . . a d co sequen tly

an d scor ifier n more lead a larger if ecessary .

n A T . . 30 ffi an d Whe of ore is used grams are su cient , A T 50 . . s with grams of lead had better be u ed .

- e e $ uartz pyrit gold ores consisting larg ly of pyrite . O w i n g to the large amoun t of lead required to scorify ores of

s u se A T this clas , it is impracticable to more than . . of ore

in on e sc or ifier sa o , so to accomplish the me result it b ec mes

n u e as s ecessary to nit the lead buttons sugge ted above . Th e ' u su a l ch arge is

Or e A T $40 . . — Gra n u l a t ed l ea d 40 45 g ra m s 1 a l a s s ) a Bor x g 74 gr m .

c or i ca tio 3. S fi n assa y of sa mp l es con ta in ing a l a r g e p er c e n tag e

o co er f pp . I n samples of this class it is necessary to use a small amoun t

of ore an d at the s a me time a l arge amount of l ead ; this is due to the reten tion of copper in t h e lead an d the diffi culty in

e n e f en n a n r movi g it unl ss a su fici t amou t of lead is used . If y

n e e n in n great amou t of copp r is r tai ed the lead butto , a high

n n heat will b e ecess ary to remove it duri n g cupellatio . This

will produce a high loss in silver value ; so it is al most imperative to add enough lead during scor ifica t ion to i n sure the removal

e e . of the copp r , wh n the silver loss will be small in comparison The usual charge is

1 Or A T . e 740 or . Gra n u l a t ed l ea d 45 or 50 gra m s

il i a n d a S c a bor x .

4 S cor i ica tion a ssa o or es a n d r od u cts u sibl e w ith . f y f p f di i u l t fl c y .

[ 1 6]

' Make the six sc or ific at ion s at on e time in the muffle as signed H ffl to you . ave the mu e at a bright red before placi n g th e

ffl I n charges in it ; when the charges are in , close the mu e door .

n a few mi utes draw the door aside slightly , and if the lead is

e n melted , remove the door compl tely and arra ge the drafts so f that there will be a strong current of air through the muf le . During the s cor ificat ion the heat should be maintai n ed at a

m n mediu orange , or a little above a good heat for cupelli g . $ ’ en d as Increase toward the to afull yellow . As soon the bull s ” e cor ifi i s s c at on . eye has di appeared , pour into a warm d mould ff When all the charges have been removed from the mu le , place six cupels in so they may be ignited by the time the buttons are

slagged and ready for cupelling .

; Cupel the six buttons at one time , feathering them all Weigh each bead separately ; part the beads together in sets of three in

$ fl . ennedy parting asks , and weigh the gold

S a mpl e A S ilver ore containing a quartzose gang ue .

- S amp l e A quartz silver ore .

a Prepare six charges of this s mple , each as follows

' A T Ol . e . — Gra n u l a t e d l ea d 30 35 gra m s Bora x gl a ss gr a m

in s r ifi r s Us e . c o e

a Cupel the six buttons at one time , fe thering them all . Weigh each bead separately ; part the beads together in sets of three in

: test tubes and weigh the gold . Record the results in this form

P er ton

m l W t Oz . Oz . A ss a y S a p e . t N Or e G S v D a e NO . o . old il er 1 T . 4 O 1 1 2 2 6 A . . ct . 940

Average the results of the as says of each sample after caleu lating them separately for each assay .

Under remarks give composition of the ore , manner of scorifying and cupelling . If there is any reason to doubt a ccuracy of the assay the .the

c m . res ults Should never , under any cir u stances , be accepted

[1 8] Describe in your notes the appearance of the s-cor ifi er s an d the W h A T character of the lead buttons . eig out . . of the ore

r i and wash on a batea , making you self fam liar with the con st ituen t s mineral and the approximate percentage of each . Use

h e IOW i e t b p p if necessary . Make a detailed report in your notes .

Follow the above directions in all future ass ignments .

A SSI GNME NT 7

$ UART$ GOLD ORE S C ONTAINING LE SS THAN ONE—HALF PYRITE

assays of this sample as follows

3 r A . T O e l . — Gra n u l a t e d l ea d 30 35 gra m s Bora x gl a ss gr a m

Us e 2 % in . s c or ifi er s and three assays

Or e A . T — Gra n u l a ted l ea d 45 50 gra m s B ora x gl a ss gra m

s 2 in s r ifi r s U e 34 . c o e .

Unite t h e three buttons from th e fir st ch arge by r e- sc or ifica tion before cupelling . Cupel the other three buttons directly _ and in separate cupels ; weigh separately for doré ; part one

h s alone and two toget er . If neces ary to add silver before part ing, alloy by means of blowpipe and dry cupel .

Note the time required by each charge a nd the size of the

b u tt On lead button . Reduce by scorifying , the size of any 2 weighing over 0 grams . Observe the following periods in scor ificat ion of sulphide ores ( consult your lecture notes )

1 H u ffl I . Melting . ave m e at a low yellow h eat . ntroduce the r ifi r ffl sco e and close the mu e door .

[ 1 9] 2 s h e . . t e en Roa ting When charges have thoroughly melt d , op the door carefully an d allow as much air as poss ible to pass

ffle n e through the mu ; if they begi to bubble , clos the door so as

Th e n to decrease the air supply . heat duri g the ro asti n g period

S e n e hould be kept at about a m dium ora g . A high h eat will

n n cause mecha ical loss by too rapid oxidatio .

$ ’

3 . e e en Fusion , or formation of the bull s y Wh the

n as an d n e roasti g has ce ed , close the door fuse dow the charg thoroughly .

4 r ifi i th . c o cat on n S . e Whe charge has thoroughly fused , as $ ’ n e e en t h e o a n d show by the formation of the bull s y , op do r

n s h e ffl n allow a good curre t of air to pa s through t mu e . Duri g this period the lead content is reduc ed and the slag becomes more fl uid .

e h e e r 5 . t e e . Final heating Wh n lead is cover d or almost cov d

th e th e a n d n e by slag , close door i crease the heat to a full y llow

and then pour into heated moulds .

A SSI GNME N T 8

$ UART$ GOLD ORE S CONTAINING MORE THAN ONE— HALF PYRITE

S a mpl e

Prepare six charges of this sample , as follows A T OT . C . — Gra n u l a t e d l ea d 45 50 g r a m s Bor a x g l a ss g ra m

in r ifi r s Us e . s c o e .

in n e t Scorify as directed previous assig ment ; cup l separa ely ,

i s e e n e . e n n e f ath ri g car fully Clean the b ads carefully , combi e s t

n d a . a of three , weigh and part ; weigh ag in Report both gold silver .

[2 0] A SSI GNME N T 9 SC ORIFICATION ASSAY OF SAMPLE S H IGHI N C OPPER

S am l e S am l e p and p A copper matte .

s : Prepare five charges of each sample , as follow

Or A T e . . — Gra n u l a t ed l ea d 50 55 gra m s Bora x gl a ss 1 gra m

in r fi r Us e 3 . sc i s o e .

1 For copper matte add gram of silica with borax glass .

n in Control the furnace as in ass ayi g ores rich pyrite . Buttons

r scor ifi ed sc or ifier s a from matte must be e ; use in . and h ve 40 total lead grams . Cupel separately the five . buttons from

n each sample , feathering the cupels at first and raisi g the heat at the end so as to ensure the removal of all the copper . Beads

ed from each sample should be weighed separately , but part together . What are the difficulties encountered in assaying ores rich in cOpp er ?

RE FE RE NCE S

— u a n : Ma n u a l o A ssa in . 290 291 . F rm f y g , pp — me t in . 6 1 P e e s : Mod er n C er S l 7 7 . t r opp g , pp

A SSI GNME NT 1 0

' S OORI E I OA TI ON A SSA Y OF ORE S A ND PRODUC T S FUSIBLE WITH DIFFICUL TY

S a mp l e Contains much antimony .

Prepare three charges as follows : A T Or e . .

Gra n u l a t e d l ea d 30— 35 gr a m s — Bora x g l a ss 3 4 g ra m s

i s r ifi r s Us e 2 34 n . c o e .

[21 ] S n th e corify in the usual man er except at end , when the heat mus t be raised to a full yellow . The buttons should be perfectly

e r esc or if Of mall able ; if they are not , y with an addition test lead . Cupel , feathering carefully ; weigh the beads separately

Part in one capsule .

A SSI GNME NT 1 1 GENERAL PRACTICE

Take the sample given you and reduce by methods suggested until you have at least two pounds pass ing a 1 00 mesh sieve ; bottle this and keep for assay .

n In this assig ment you will be given three or more ores , in

n addition to the one sampled . You are to determi e their com position and then decide on charge you would use for assay by

ifi ion s cor cat method .

Make a detailed report , indicating the composition of each sample , the charge used , etc . Give both gold and silver values

[22 ] CHA P TE R I I I

CRUOI RL E ASSAYS A S S I GNME N T 1 . 2

DE TERMINATION OF GOLD AND SILVER IN LITHARGE THE S H OF REDUCING POWER OF C ARCOAL , A SS ARGOL , AND FLOUR , AND AY OF FLU$ E S

s Before making any assays , the a sayer should determine the

r precious metal content of the litha ge used . Litharge contain ing more than a trace of gold should be rejected . The presence of a small but uniform amount of silver is rather an advantage O than therwise , as the silver serves to help collect the gold . The ass ayer must also determine the reducing powers of the various reducing agents ; and an assay of all the reagents used $ ” fl should be made in order to detect any salting of the uxes .

F ir t r s . To dete mine the precious metal content of the r f litharge , prepa e two charges as ollows

L itha rg e 1 00 gra m s A rgol 2 gra ms

a l e S t cov r . i l Us a . u e No 7 cr c b e .

add To one charge , a small amount of test silver . Fuse

n quickly both charges in a hot fire until thoroughly liquid , the withdraw and pour ; cupel the resulting buttons . Determine gold and silver by weighing the unalloyed bead for the doré , and parting the other for gold . If more than a trace of gold is

S found , the. litharge must be rejected . Note the ilver content , and correct all assays according to the amount of litharge used .

F or example 1 0 00 5 m . S . ilver in grams of litharge weighs g , litharge used 60 m in assays weighs grams , doré bead weighs g . , then m g . , and the corrected doré is or

mg . [23] e o e n S c n d . To d termi e the reduci n g pow ers of the reducin g

n fl r e : age ts , argol , our and charcoal , p pare charges as follows

A rg ol 1 g ra m Sil ic a 30 gra m s L itha rg e 75 gr a m s Sod a 25 g ra m s

a e Bor x cov r .

Us a u i l e . e No . F cr c b

u s i u e a l S b t t t for rg o , Fl ou r 1 gra m

3 . u s i u e a l S b t t t for rg o , Ch a rco a l 1 g ra m

n Reducing age ts , only , should be weighed carefully . Fuse ,

on e e e at tim , the above charges ; wh n qui et , pour into clean , warm

a a n d . sl g moulds . Clean weigh the resulting lead buttons

n e 1 0 Weigh , usi g pulp scales , to the near st mg .

Note that the above determi n ation s are made under normal

n n n w orki g co ditio s .

T i fl e h r d . s To make an as ay of the uxes us d , prepare charge , as follows

S il ic a 30 g ra m s L ith a rg e 75 g ra m s Sod a 25 g ra m s Bora x gl a s s 5 gra m s

R u 1 8 - a u n e d c e r for g r m b tto .

l n S a t a d Bora x cov e r .

s u i l e U e a No . F cr c b .

Add a weighed amoun t Of test Silver to the charg e and f use i e n h e S . t usual way Determine gold and ilv r , if any

[24 ]

Sufficient reducer should be used to produce an 1 8—25 gram lead button . If the ore is oxidizing , several grams of reducer

s n may be nece sary . If the ore contai s more than about 1 0 p er

n cent pyrites and no oxidizing age t , reducer will be at a mini mum and a small amount of oxidizer as nitre may be necessary . An ore containing more than about 1 5 per cent pyrites cannot be properly treated by this charge Other reducing agents which may be used $ instead of flour are argol , charcoal or sugar Prepare three charges of Sample using the charge

s i given before and an F crucible . This sample consist ma nly of

5 n an d quartz with less than per cent of sulphides of iro , lead copper, and reduces grams of lead per one assay ton of ore .

Unles s the proportion of S ilver to gold in an ore is kn own to

as s S S d be at le t five to one , te t ilver houl be added to all charges except one . Weigh the test silver added to one of the charges .

l w e t w o This il ustrates three methods of workin g . and have

S checks on the gold and two on the ilver . The amount of silver

' in the litharge will of course be dedu ct ed f r Om the weight of the doré .

On one charge use a salt cover , on the others a borax cover .

H s h eat the charge until in quiet fu ion , then increase the eat

s n . to low yellow for about five minute , or u til the charge becomes

ds an . d smooth on top Pour into clean , warm slag moul , when co l O break away the lead button ; clean , hammer into cubes , and then cupel in the usual manner . Report results in the following form

Per t on Gold A ss ay S a mpl e Gold S il ver Gold S il ver m z z m . o . o . e r z N N Or e D . o . o . o . ore g g p

1 483 1 A . T

Under remarks indicate everything that h as a bearing upon l e a . the results . Describ the appearance of s g, buttons , etc Which ? cover do you prefer , and why

[26] i A T Make a vanning test of the ore , us ng about . . of ore l . s t and a batea Report this te a so . A T If neces sary to use . . of ore or to make the fusions in a

ffl : mu e , the following charge will be found suitable A Or e . T

L ith a rge 60 gra m s Soda 2 0 gra m s Bora x gl a ss 5 gra m s

R u i a 20 - ra n e d c e r to g v e g m b u tto .

u n Gro d bora x cov e r .

Us a u i l e e No . F cr c b Prepare two charges of Sample using the above

a charge . Add weighed amount of test silver to one charge , and

n n S an u weighed amou t of test ilver to the other . Make the usual

tests , and fuse as before . mix To any charge , put the soda into the crucible first , then fl mix the litharge and other uxes , lastly the ore , and all together

O with a fork ; S prinkle salt or borax over the t p . Make certain

fl x th or ou h l the ore and u es are g y mixed .

A SSI GNME NT 1 4

NITRE ASSAY FOR ORE S C ONTAINING MODERATE AMOUNTS OF PYRITE

Ores of this clas s are usually richer in gold and silver than

‘ t an d con se u en t l ma hose of the previous class , q y less material y

be taken in assaying them . The following charge will be found suitable for ores of this c lass : A Or e . T

L itha rg e 90 gra m s Sod a 20 gra m s Sil ic a 1 0 gra m s Bora x gl a ss 5 gra m s

i n el i in a N tr e a ccordi g to pr m ry . Cov e r

fl in Us e a 7 u x . No . g pot

[27] ' ch ar es sh ou l d e as Fusion of the g be carri d on before . Calculate the amount of n itre (see below ) to add so that a

20 - T n A . gram butto will be produced from . of ore . Make three a says of Sample using the charge given

n above . Sample contai s about sulphides .

S on e e m n Add test ilver to all charges but . B fore com e cing

e t work on this assignm nt , be sure tha the previous one is

n e thoroughly u d rstood . Th e reducing agents which are common ly presen t in ores are

n n n a timony , zi c , arsenic and sulphur . Iro pyrites , the sulphide

n as commo ly met with , reduces follows Fifteen per cen t of pyrite will reduce about ni n eteen grams

n o e n 1 5 er n Of of lead , and there will be excess . Mor tha p ce t A T e n e . pyrit , usi g . . of ore , will reduce too larg a lead button

e e n t h e S e n Nitre , an oxidiz r , is us d to co trol ize of the l ad butto , an d is usually stated in terms of lead ; that is , one gram of nitre

e s n n oxidizes four grams of lead , more or l s , accordi g to conditio s .

n as In order to k ow how much nitre to add , so to reduce ,

20 - n w e e e within a few grams , a gram lead butto , must d t rmine or guess correctly the amount of lead which will be reduced

n before maki g an ass ay . The reducing power of a sample may be determined by making

: a preliminary , thus

S a mpl e L itha rge

a l S t cov e r .

N fl xin s e a o 7 u . U . g pot

H ave the fire hot when the charge is put in an d fuse quickly ;

’ i r n n n e h e en n emove a d . a d t wh quiet fusion , , pour Clea w igh button . Calculate the amoun t of n itre which must be used on a basis

n of one gram of itre to four grams of lead . I n prepari n g charge of Sample add to on e charge gram more nitre an d to the other gram less nitre than the

n n e an d calculated amou t . Weigh the resulti g l ad buttons ,

n n calculate the oxidizing power of nitre u der these con ditio s .

n Compare this res ult with the amou t used above . [28 ] A SSI GNME NT 1 5

NITRE ASSAY F OR ORE S C ONTAINING LARGE AMOUNTS OF PYRITE

$ as in Material of composition indicated above , is general ,

n assayed in the same way as that of the previous assig ment . Th e increase in the amount of iron pyrites calls for an increas e

of litharge to complete the oxidation ; and as the amount o f

silica in the ore is decreased and the charge becomes more basic ,

n - e more acid in the form of silica or wi dow glass must be add d . The following charge will suffice

Or e

L ith a rg e 1 2 0 g r a m s Sod a 2 0 gra m s Sil ica 1 5 gra m s Bora x gl a ss 1 0 g r a m s

i e a in el i in a N tr ccord g to pr m ry . a l a e S t or Bor x cov r .

Us a 0 - i e . 3 a u l No F or g r m cr c b e .

20 Calculate for gram button .

When the material to be ass ayed is a pure concentrate o r nearly so , the amount of nitre to be added can usually be placed 25 A T t s . . u at abou gram for . of ore For material of nknown

n percentage of pyrites , a prelimi ary assay must be made .

In general , ores of this type are richer than the type treated

s n 1 4 in As ignme t , and a smaller amount of ore can be assayed , thus effecting a saving in time and fluxes ; when a sensitive

e d balan ce is available an d the values are uniformly distribut .

. 1 A T s . . the result obtained by using a smaller amount , 4 , will A T be even more accurate t h an z t h ose from . .

[29] en 1 A T following charge will do wh 4 . .

Or A T e .

L ith a rg e 75 g ra m s Sod a 1 5 gra m s Sil ic a 5 gra m s Bora x g l a ss 5 gra m s

i e a in el i in a N tr ccord g to pr m ry . a l a S t or Bor x cove r .

Us e a 20 - a u i l gr m cr c b e .

1 6—20 Calculate for gram button . The ore to be assayed in this assignment is a concentrate obtained from one of our mill runs , and is a typical concentrate .

A . S T . Prepare three charges of ample using , and

A T . three using .

s Time required for fusion about thirty minute , ten minutes

. n as yellow heat at the end Avoid heati g too rapidly , a sudden , uneven heating may cause the assay to boil over

s as Report the mean of the several a says the correct value , first discardi n g any assay that appears to have been abn ormal in any manner

A S SI GNNIE NT 1 6

ROAS TING ME TH OD FOR ORE S CONTAINING LARGE AMOUNTS OF PYRITE

- Obtain two 4 inch roasting dishes with covers . Line each

_ dish thoroughly by rubbi n g a blackboard crayon over its interior .

A T S n . Weigh out . . of ample i to each dish Place ffl the dishes , covered , in the mu e , which should be heated to low

n ma t er ial redness on ly around the edges and cor ers . The to be roas ted Should be spread out in the roasting dishes an d ridged

as . across , so as to expose as much surface possible to the air

- After one half hour, take out the roasts , letting them cool a

$ little before removing the covers ; then turn the ore over with a wire provided for the purpose , leaving it spread about and

[30] as . ridged , before Return the dishes , without covers , to the mu ffie t - , if the heat is s ill low . After one half hour take out and

n n s stir again . Co tinue this treatment , gradually i crea ing the

e on n heat , till no odor of sulphur dioxide is perc ived stirri g .

s Finally, increa e the heat to a bright red for about ten minutes ,

n to d ecompose a y iron sulphate which may have formed .

Smelt the roa sted concentrate with this charge :

l cru cib e .

After the concentrates have been transferred to the crucible , $ ” as n S - the ro ti g dish hould be dry washed out with a little soda ,

a which is added to the ch rge .

Compare results with those obtained from the nitre assay .

A SSI GNME NT 1 7

ASSAY OF SULPHIDE ORE S BY THE NAIL ME TH OD

$ ” The nail method is adapted to gold ores containing vary

n e n modifi ing amou ts of sulphid s , although it may with certai cations b e applied to all gold ores . Ores containing appreciable amounts of arsenic an d antimony can not be as sayed by this

ce n : n n method , with this ex ptio arse ic frequently occurs in va ner concentrates and may then be removed in the first stages of the

oxida iOn a assay by t with nitre , p rt of the sulphur being oxidized at the Same time .

e g In gen ral , gold values will be hi her by this method and S ilver values lower

[31 ] Prepare charges of Sample as follows :

Or e A . . T

L ith a rg e 30 g ra m s Fl o u r gra m s Sod a 45 g ra m s

a l a e S t or bor x cov r .

T n - en n n il s hr e e twe ty p y a . i l s e a u e . U No . F cr c b

' Add a weighed amount of test silver t o ea ch charge

Stick t h e n ails i n to the charge after the borax cover h as been

n n . S n en added , poi ts dow hould the ails first added be eat up

e e n n e a e by the charg b fore fusio is fi ished , tak out wh t r mains

th e n an a of old o es d dd two or three fresh ones .

‘ First fuse th e charges in the usual way ; when foaming has

s t en cea ed , give a very bright yellow heat for or fifteen minutes ,

n n t h e h n n e n t h e conti ui g eati g u til , on r movi g nails and rinsing

in e n them the slag , th y are seen to be free from adheri g globules of lead .

Prepare one charge of Sample as directed for Sampl e

5 1 ad except add grams 8 0 and d no test silver .

Prepare two charges of Sample as follows :

A T . Or e .

L ith a rg e$ 25 gra m s Sod a 45 gra m s Bora x gl a ss 1 0 gr a m s Sil ic a 1 5 gr a m s

- n n il s Fiv e twe n ty p e n y a . S a l t or bor a x cov er

N u i l e Use a O. F cr c b

Make the fusion as instructed before .

When arsen ic is presen t it is w ell to omit t h e nails add 1 0 $ to 20 grams of nitre and boil dowp t h e charge ; then add th e nails an d fin ish at a high heat as usual .

[32 ]

CHA P TE R I V

BUL L ION ASSAYS

f cl assified as Bullion , in general is follows

1 - . s Lead bullion , usually the product of the lead bla t furnace ;

95 n per ce t and more lead , containing some copper, antimony ,

et c . S , ilver and gold .

2 1 00 92 . 5 S Base bullion , containing from to parts of ilver 1 000 per , gold in varying amounts , and a large percentage of

a fl b se metals , chie y copper , zinc , lead , etc . Produced most

s frequently by cyanide mill .

3 925 990 . Doré bullion , containing to parts of silver per

1 000 s , some gold , and ba e metals , mostly copper , but also lead , antimony , zinc , etc .

4 990 1 000 . Fine silver bullion , free from gold , containing to 00 S 1 0 a e . parts ilver per , but some b se m tals , usually copper

5 n n an d . Silver bullio , contai ing little base metal less than half its weight in gold .

6 n n . Gold bullion , contai i g little base metal and more than half its weight in gold .

990 7 . S Fine gold bullion , free from ilver , containing from to 1 000 1 000 parts gold per .

You have had practice in assaying lead bullion (see Assign ment Gold bullion and fine gold bullion may be con sidered under a general case ; likewise base bullion , doré bullion , fine silver bullion , and silver bullion

it l n Fu ton : Ma n u a l of A ssa yi g .

[34] A SSI GNME NT 1 9

ASSAY OF GOLD BULLION

The bullion that you are to as say in this assignment is made to represent as closely as possible that which comes from Cali f or n i a mines . — Th e P r elimin a r y I n this clas s of bullion an expert ean tell with sufficient exactness the fineness of a particular sample and 1 so can alloy in the proportion of to , without making a

as n preliminary survey . Ordinarily the b e metal fi eness is not Of taken into account , a small amount copper being added to the t proof center to prevent sprou ing, and to toughen the bead .

a But , for the general c se , and , for completeness , a preliminary as say must be ma de in order to d etermine the approximate fin e

s ness of gold , silver and ba e . 90—1 00 00 Weigh out mgs . of the bullion givenyou ; also 3 mg s . of test silver ; wrap silver and bullion together in 3 grams of

S heet lead , and cupel at a little above the feathering point . l a Brighten wel ; cle n , and part the bead .

Report the results according to the f ol l oWin g example

B u l l ion t a k en T est sil v er

B u l l ion a n d t est sil v e r Cu p el l e d b e a d

B a s e m et a l Gol d ( b y p a rtin g) Silver ( b y differen ce )

These results Should be corrected by adding 1 5—20 points to the Silver fineness and substracti n g the same amount from the

a S b se metal fineness . This is to allow for ilver lost during cupellation

[35 ] Havi n g determin ed the approximate fineness of the bullion

500 n given you , weigh out two samples of mgs . each (withi 05 1 . S n 0 also weigh out test ilver ( withi . mgs . ) so that the ratio of silver to gold will be to 1

Make a proof center of pure gold silver a n d copper to

n correspo d with the regular samples .

e 6 ee as n Wrap ach sample in grams of sh t lead , or ma y as

n n 900 the followi g table calls for . For bullion co taining over poi n ts of precious m etal 5 grams of l ead are suffi ci en t to remove f s e d r mi all the ba e metal . The following tabl is valuable for et e n ing the least amoun t of lead to use

P r ec io u s Met a l in A lloy 900 8 00 700 600 500

Cu el l a tion — n n fle p Before i troduci g the samples into the muf , have the t emperature at a bright red (high e r than for or din ar v

S . cupellation ) , and the cupels , which hould be smooth , hot

e in Place the l ad p ackets their respective cupels , the proof i d n h e fle n a n t . the center , the close muf door As soon as they

n uncover , ope the door and allow the cupellation to proceed in the usual manner . l Take care that no metal is sticki n g to the S ides of the cupe s .

w Brighten the cupels at a bright red heat , cover ith hot cupels and remove gradually from the muffle . Clean carefully and weigh .

n n Now hammer the beads i to the shape of a recta gular bar, then roll out to the thicknes s Of an ordi n ary visiti n g card by

n in n n mea s of the rolls ; or the abse ce of rolls , hammeri g will do .

I n n a n W e an d rolli g , n eal the alloy henev r it becomes hard elastic

Mi el l : Ma n u a l o A ssa in 61 0 tch f y g , p . .

[36] n et Th e b e and before it begi s to g rough on the edges . three ads

S n hould be of the same thick ess after rolli n g . Great care Should b e en taken to prev t mechanical loss .

‘ t n — P a r i . ean fl s . 2 g Cl thoroughly three matrass a ks Place ozs .

s . n ew fl e of p . gr nitric acid in each ; introduce the att ned an d e annealed b ads , first rolling them into a spiral coil , and

n heat to boili g .

e n Boil g ntly u til action ceases ( ten to fifteen minutes ) , then 2 n an . s pour off the spe t acid d add ozs of strong acid p .

n Boil gently with this acid for fifteen to twe ty minutes . Place a piece Of charcoal or burnt br ick in each flask to preven t

u off bumping . Po r this acid and wash the gold three times in hot water . Transfer to annealing cups and anneal .

Weigh the gold carefully ; and record the results according to the following example

S a mpl e A Proof c enter S amp le B

mg . mg . m g .

mg . mg . mg . 5 7 mg . 6 g ra m s 6 gr a m s 6 gra ms i m S l v e r mg . g . mg . m m mg . g . g .

' m Cu p el l a tio n l OS S g . P roof c en t e r l o ss

mg . mg . m mg . mg . g .

mg .

S u rch a rg e

Corr e ct e d g ol d B a s e m et a l Sil v e r ( b y d iffe ren c e )

Sil v er fi n en es s B a s e m et a l fin en ess Gol d fin en ess

[37] — Rema r ks 1 n Gold results should agree within 4 poi t . Silver

i n as . results w ll depe d on the care used in cupellation , will the a b se metal fineness . Surcharge is the differen ce between gold los t during cupellation and parting ( gold may be los t by

n n volatilization , cupel absorptio , or solutio in the acid ) a n d the

e e in te n amount of silv r retain d the par d . It is ge erally positive .

e A negative surcharge is to be regard d with suspicion . In order to get precise results it is necessary to have pure

as - - gold for the proof ; parted gold from previous says will do , but 1 1 then an arbitrary surcharge will have to be used , say 4 to point . a When rolls cannot be obtained , the gold bullion ssay may be made as follows :

1 . Make a preliminary assay as usual .

2 0 00 2 5 . 5 . . Weigh out mgs of bullion , instead of mgs , and a dd sufficient test S ilver to make the p r Op or t ion 3 to 1 . Make up the proof in the usual way .

ds fl at After weighing the cupelled bea , hammer until anneal

n s . . n s and part , usi g acid of p gr Boil for five mi ute , decant ,

e an d . was h three tim s , anneal weigh

This method has the advantag e of being much more rapid than the former and at the same time , if carefully done , is sufficiently accu rate

RE FE RE NCE S

462—49 R s e : Met a l lu r o G ld . 2 o g y f o , pp

A n in a 2 30—47 a : A ssa . . ro y g , p rt , pp

$ ” in l n il in h in in n P a : A ss a a d e t e M M . a d ck y g of Go d S v r U S t,

S ci. P r ess . 1 4 1 903. , Nov , ” W i e ea l e : T h e a lin a n d A ssa in l u lli n T h e h t h d U k mp y g of Go d B o , S g ’ E n in eer in n Min in r n F 1 2 1 898 a d $ u a l eb . . g g g o , ,

[38 ] A SSI GNME NT 20 FIRE ASSAY OF SILVER BULLION

Make an ass ay of the sample of S ilver bullion obtained in ’ n 22 o Assig ment , f llowing the directions given in F u lton s Ma n u a l o A ssa i n f y g . Record results according to the following example

P RE LIMINARY A S S AY

u l l i n 500 B o mg . L ea 1 0 d grm .

Cu el l e ea p d b d mg . P a rt ed gol d n on e

il e b e u s e in 445—450 S v r to d proof mg . Gol d to b e u se d in proof n on e

C e b e u s e in 50— opp r to d proof 55 mg .

FINAL A S S AY

S a mp le A Proof B u l l ion 500 mg il e S v r mg . Gol d in proof n on e

C e in 52 opp r proof mg .

L ea d grm . grm . grm .

l a n d S il in Go d v e r mg .

l l . Cu e a . p e d b e d mg mg . mg

Cu el l a n l s s p tio o mg . P roof c en t er l oss

B a s e m et a l P a rt e d g ol d n on e

B a s e m eta l fin en e ss Gol d fin en ess Sil v er fi n en ess

1 000 1 000

in n r Use the utmost care cupelli g . Do not neglect to cove the cupels with h ot cupels when the beads have brightened ; a

' bead that h as sprouted must b e discarded and the entire assay r 6 eat ed p RE FE RE NCE S 1 — 1 n 75 77 . u l n : Ma n u a l o A ssa i . F to f y g , pp — u a n : Ma n u a l o A ssa in . 2 76 2 80 . F rm f y g , pp [39] CHA PTE R V

MI SCE L L A N E OUS WOR$

A SSI GNME NT 2 1

$ FURNACE REPAIRS . MA ING CUPELS

1 . a r e You are assigned to a particular furnace , and you

e e in n xpected to ke p it repair . Exami e it carefully ; especially s ee

ffl i d on di ion n oo c t . an d that the mu e is g If it is not , remove it

in n e n n n put a w o e . The followi g poi ts should b e considered in

placing a new muffle : Have the muffle well supported in the back

a n d S n n n front , give it a light i cli atio downwards toward the

e e en n e th e n front , and hav the c m ti g mat rial of right consiste cy . — Fire clay with a certain proportion of san d or b r oken tire -brick

en n e is the cem ti g material us d .

Make up t h e cement in t h e following man n er : Take fir e- clay a n d fi r e- in t h n fi r brick e proportio of one to three . Crush the e

s a n e en e e brick to pa s ight or t m sh scre n . Mix the two dry and

e n e in n then add wat r u til the whol is a plastic conditio . Moisten thoroughly the brick - work a n d those portions of the muffle that

in n t h e a n d come co tact with clay , then press the clay in firmly

- allow to dry at leas t twenty four h ours .

n n e Make a drawi g ( pla and s ctions ) of your furnace , to scale .

2 200 s . e a Mak good cupels , follows

e an d — Take the box us d for the purpose fill with bone ash ,

n n e add water and mix . Use as ma y ou c s of water as pounds of

- n b n en bone ash . The right amou t of water has ee added wh the

- s its a e n a n d e bone ash lose h rsh , gritty fe li g , at the same tim is

$ n n t 2 not pasty . A small amou t of potassium carbo a e ( per cent

n ma e s n on - solutio ) y be add d to as ist in ceme ting the b e ash , but

en n e- this is not nec essary . Wh the bo ash is thoroughly mixed a n d th e n n S s e is of right co siste cy , ift through a twenty me h si ve

n d n f en n in a the place a su fici t amou t the mould , and hammer down firmly ; two hard blo w s a r e en ough ; do n ot use an ythi n g but the wo od en mallet in striki n g the mould . Place your cupels on a board an d set away to dry .

[40]

A SSI GNME NT 23

COMPARISON OF ME TH OD S FOR ASSAY OF COPPER ORE S AND COPPER—BEARING MATERIALS

or i c tio — S c fi a n . The standard charge for the assay of Copper ores and copper bearing material by the s cor ificat ion method is as follows

r e A T A T O . . to . Gra n u l a ted l ea d 50 g ra m s Bora x gl a ss 1 g r a m Sil ic a 1 gra m

3 in r ifi r s Us e . sc o e .

' Re - s 2 1 scor ifier s scorify lead buttons , u ing /2 inch and enough a 35 test lead to m ke total weight of l ead not less than grams . When the ore or copper-bearing material is poor in copper the

a n d r e - s or ifica ion s silica c t may be omitted . As many assay may be run as are necessary to give accurate results

Cupel and slag corrections , either or both , are sometimes required an d may be made as follows :

The cupels are taken in lots of two each , the unused portion 1 00 discarded , the remainder crushed to pass mesh , and fused

1 00 e 20 40 m with grams of litharg , grams sodium carbonate , gra s

an d 3 . borax glass , grams of argol

n 1 00 e The slag is merely grou d to pass mesh , and fus d with

sa 40 20 Of the addition of , y , grams of litharge , grams sodium carbonate and 3 grams of argol . In both cases the res ulting lead buttons are cupelled and the silver and gold obtained added to the first weights Cr u cibl e — A standard method for the ass ay of the above by the crucible method is as follo w s :

1 Or e 730 to A T L ith a rge 80 gra m s Sil ic a 1 2 gra m s

1 6 a s Ca . Sod . rb gr m Bora x g l a ss 1 2 gra m s

Redu c er or oxidiz e r f or a 20 g ra m b u tton

s e a u i l e U No . F cr c b . [42 ] For ores or oth er material containin g less than 40 per cent

n a 1 A T copper, the amou t used for ssay may be increased up to A; . . l l S Some or a of the ilica may be omitted . Prepare eight charges of Sample a copper matte rich in copper , according to the methods already outlined, four

scor ificat ion by and four by crucible fusion . Use proper pre

in cautions melting and cupellation . n a Make a tabular report , showi g comp rative losses , etc .

A S SI GNME NT 24

I N A ND PRAC TICE SAMPLING , PANNING AMALGAMATING

i $ S a m lin — Take ‘ th W p g g e sample of ore given you; eigh , and then reduce in size (weight and mesh ) by a pp r oved methods .

$ u s o S Yo r a say sample Sh uld weigh at least lb . and hould pass at 1 00 - s s . e t least a mesh screen , Take car tha all scale pa s the screens used .

Reserve all discarded ore passing the 40- mes h screen and keep f r o the panning and a malgamating experiments .

[ f A ma lg a ma tin g fi — Weigh out five charges ( 1 00 grams each )

' 40- I b ot tl es r ovided of the mesh lot , and place n p for the purp ose . r 1 0 1 0 an d 5 c c . with mercu y ( grams ) , and of water ; agitate for thirty minutes . Separate the mercury by panning (see below )

an d e t . transf r to a porcelain dish , dry with filter or blo ting paper Place the thoroughly dry mercury in a 20 gram or F crucible

20 t o e in which grams of lead have been placed . Add the crucibl

n 30 a 1 0 a s a charge co sisting of gr ms of litharge , gr ms of oda ,

5 s e grams of borax gla s , and grams of argol , and silver nough to part th e gold .

n Fuse the charge very slowly, starti g with a slow fire in the

ffl h as wind furnace or if using a mu e , one that not yet become

’ i n u l n s A mod fic a tio of F to m ethod .

[43] red and has a good draught through it . to preven t the escape

. n of fumes into the room When fusio is quiet , pour and cupel

an d the resulting lead button . Part weigh the gold .

P a n n in g — The content s of the bottles are to be panned separately and then together . Pour the contents of one bottle

n s n i to a gold pan , add water if necessary, and wa h by givi g the ff pan a vibratory motion as in vanning , washing o the light particles of gangue an d leaving on ly the mercury and the heavy

an et c . portion of the ore , as black s d , sulphides , The light portion of the ore Should be washed into a pan or vessel of

an n somewhat larger size than the gold p . Repeat the pa ning of

’ an d n the mercury co centrates in order to separate the mercury . fl If the mercury is oured , add a small globule of liquid sodium

amalgam .

s Treat the contents of the other bottle in the same way . The light portion or tailings of the several bottles may be poured

n Re - i to the same vessel . pan this material to make sure that n o e an mercury or sulphides have scaped . If y is recovered , add to the amou nt recovered before .

Treat the collected mercury as directed above ( see amalga mating) .

OR an d Allow the tailings to settle , pour the surplus water,

as dry by any convenient means . When dry, weigh , p s through

1 00- s a mesh screen , mix well and a say .

W as h the heavy material or concentrates into a small por l i c e a n . pan , or if more convenient on to a batea Examine under

a magnifying glass or low power microscope , and note the

difi er n Of e a r oxi e t kinds sulphid s or other constituent , and the pp

mate amoun t of each .

1 00- s e an d s s Dry , weigh , crush to pass a me h scre n , a ay

From your results calculate the following

1 n t en . . Assay value of ore in ou ces , and dollars and cents per

2 an d e t en . . Gold amalgamated in ounces , dollars and c nts per 3 . Assay value of concentrates in ounces , and dollars and

n c e ts per ton .

[44 ] 4 Assay value of tailings in ounces , and dollars and cents p er

5 . Percentage of gold amalgamated . 6 . Total gold contents in comparison with assay value

1 ff n . Percentage and di erent ki ds of sulphides or other h eavv mate r ial

RE FE RE NCE S

l n Ma n a A — — u : u l o ssa in . 36 4 l a n 1 54 1 5 F to f y g , pp d 6.

u a n : Ma n u a l o A ssa in a 2 F rm f y g , ch p . .

n : Ma n u a l o A sa in 1 — 4 s . 85 1 Brow f y g , pp 9 . $ ” H er sa m : P in i l e s in t h e P a i e a l n Min n r c p r ct c of S mp i g, . a d W ' r ld . 25 1 91 1 o , Nov , . $ u n n : M e n P a i e in Or e a l in Tr n A m n t t a s . . I s t . Min Br o od r r c c S mp g, . E n l 40 vo . . 56 g , , p 7

H a n : T h e Met a l lu r o L ea d a V ofm g y f , ch pt er .

A SSI GNME NT 25

FIRE ASSA Y OF LEAD ORE S

s fl Lead a says are usually made in the muf e ; but , in the absence ffl f , . o such a wind furnace may , be used The mu e is to be preferred because the heat can be more uniformly controlled , and there is less danger of loss by volatilization . ffl All our lead assays will be made in the mu e furnace .

The fire assays of lead ores may be placed under three heads , according to the kind and proportion of flu x used

1 n . . Fusion with sodium bicarbo ate , borax , argol , and iron

2 s . Fusion with mixture of sodium bicarbonate and pota sium carbonate , borax , argol , and iron . i 3 . . Fusion with potassium cyan de

S amp l e Pure assayers litharge .

[45] Prepare three charges as follows

Or e 1 0 gra m s L ea d fl u x 35 gra ms S a l t cov e r

Us e B a tt ers ea P cru cibl es

Manage heats as directed below ; pour into scor ificat ion moulds .

a n d Clean buttons by brushing hammering . Weigh on pulp 01 . . 1 0 balance to gram Report to . per cent .

S am l e n p Pure Gale a .

e Prepare three charges as b fore , with the addition of four nails to each crucible , and five grams of borax glass on t Op of each charge before salt cover .

Assay Sample in the same manner

s 5 Your re ults should check to within . per cent . Write your notes carefully .

The lead flu x is a mixture of sodium bicarbonate ( 1 2 parts ) s 1 2 s 3 potas ium carbonate ( part ) , argol ( parts ) .

The first method should b e used on ly when potassium car

n n l e bonate ca ot be procured . The third shou d be us d only on

n in pure ores . The seco d is preferable all cases

H ea ts — The fusions are b est managed by giving a low h eat

b n s an d for a out twenty mi ute then a high heat to finish . This is necessary for two reasons : ( 1 ) Lead and its compounds are volatile ; and if the heat is so high that boiling takes place 2 violently , some lead is almost certain to be lost . ( ) Lead forms a double sulphide with sodium; an d to reduce this by mean s of is iron , a high heat necessary .

Th e nails should not be removed until entirely free from lead .

Fusion with cyanide requires a very low heat .

RE FE RE NCE S

a n : T h e Met a llu r o L ea d a e V . Hofm g y f , ch pt r —201 u l n : Ma nu a l o A ssa in . 1 99 . F to f y g , pp

[46]

T HI S B OO$ I S DUE ON TH E L A S T DA TE

A N I N I T I A L F I N E O F C E N T S W I L L B E A S S E S S E D F O R F AI L U R E T O R ET U R N H D U T H THI S B O O $ O N T E D AT E E . E P E NA L TY W I L L IN C R E A S E T O s o C E NTS O N T H E F O U RTH D A Y A N D T O O N T H E S E V E NTH DA Y O V E D R U E . SEP 1 4 19383 VI 7 1975 SE? 1 5 1932

950 1 0 1933

UN 7 1 1976 4

L D 2 1 —2 0 m