Crystallography of Stibnite and Orpiment From

CRYSTALLOGRAPHYOF STIBNITE AND ORPIMENT FROM MANHATTAN, NEVADA Cnnnr,rsPer,ecnn RNn Devrn Monnll, Hantard.Ilni.aersity.

Srrnnrrr The following quotation from Ferguson describes the various modes of occurrenceof stibnite in the White Caps Mine.

365 366 THE AMERICAN MINERALOGIST

Frc.1. Stibnite. Fro. 2. Stibnite TOARNAL MINERALOGICAL SOCIETV OF AMEMCA

Frc.3. Stibnite.

Frc.4. Stibnite. Frc.5. Stibnite. 368 TE E A MERICAN MIN ERALOGIST

Frc.6. Stibnite. Frc. 7. Stibnite. Drawn with side prnacoid in front. JOURNAL MINERALOGICAL SOCIETY OF AMERICA 369

(c) short crystals with more or less complex pyramidal terminations. These are very similar in habit to the average crystals from Ichinokawa, Japan. They are shown in figures 3, 5, 6, and Z. Thirty-three crystals were measured, some of them by both authors, and revealed a very complex form series with three well established new forms. Since the crystallography of stibnite has been very carefully studied recently by NefiB there seemed to be no occasionfor a general discussionof the form serieshere. A list of the forms observed is given in the following table together with a table of combinations.

1. Tesln or.rrre Fonusor, SrrgNrrp rnou Mexnlrtm,r. Nrvloe. Listof Forms:

Letter Symbol Frequency Letter Symbol Frequency

b (010) Every crystal p (111) 2 crystals a (100) 3 crystals (113) 20 crystals d. (12.1.0) 4" It (114) Lu h (310) l4 IJ (227) ls n (2r0) 14 .l b (116) ?s L (s20) 4" K (23s) 24t R (430) I4 I (313) 1( n (110) Everycrystal a (343) 21 4 d (230) 7" 1l (3s3) l4 o (r20) 124 6 (2r3) 10u .. q (130) 14 n (243) 134 (140) 64 b (2s3) 144 0 (160) 1u t (263) 44 @ (r7o) t4 c (27s) 104 L (180) t,, e (283) 2" JV (023) 3" (2e3) 3" L (103) 34 v (r46) L" (101) 10 .. e (r2s) 104 3aD. .l (s03) 22 M (413) I" (s.11.3) 14 m (s.10.3) 3n T (s21) l( a. (4.10.3) l" o (e.10.3) 4u *rI, (673) 7" *a, (42s) 6c

+ indicates new form. 370 THE AMERICAN MINERALOGIST

2. Tesrr or CoMstNlttoNs' l. b, m,s, r' Slenderneedles. Figure 1' 2. b, n, m, Q.. Figure2. 3. b,m,r,b. 4. b, m, s, K, r. Figure3, a, b, c' 5. b, m, Q.,s. 6. b, m, (D.,s, K, A. . Figure4. 7. b, m, tD.,s, KrT, o. 8. b, n, 4 m, Q,,s, KrII. . 9. b, d,, n, r, k, fl,,qrr- 10. b, tn, Q.,s, K, r, e . ll. h, a, d,.,n, frt,o, q, i'rr ' Figure5. 12.b, m, d., o, q, K,r,b. 13.b, m, Q., K, a,n,b,C. 14. b, m, L, z, s,r, d, n, b. Figure6 approximately' lb., rn' 75. bi,n, L,ffr, z, K, r, s, o, nrl'' erb, . 16. b, n, /n, ot q, z, lh.,K, r, n, T, M, erg, b, II', C'

There are doubtless other particular combinations of the many forms present. It will be noted that the prism series is very rich in forms. The new orthodome (503) is present on two-thirds of the measured crystals and gave excellent readings in good position' The two new pyramids, although not so constant in position, were present on so many crystals that they are regarded as well established. The measurements for the new forms are as follows:

No. or Clt,cut rttro Mrlsunro Lrurrs Cnvs- F p 6p Qp TALS o

(s03) 90000' 59"40 goooo'59o40 15 10 59o36'-59o47' (67s) 40o48',7201940"53'72"24 11 a 10035'-410I 1 Tz"o5'-72"40' (42s) 63o36'42"29 63"36'42"13 11 i2" 37',-.6202541"31'42"39'

Of the many pyramids the most prominent is r (343) which appears in all the drawings and is present on two-thirds of the .IOURNAL MINERALOGICAL SOCIETV OF AMERICA 371 crystals. As this form is also the dominant form on the stibnite of Japan, there is a striking similarity between the crystals from the two localities. Indeed the whole form series of the Manhattan stibnite shows a distinct parallelism to that of Japan. Had the more complex crystals been drawn, such as combinations 18 to 23, the similarity would be still more striking. fn view of the many crystal figures of the Japanese stibnite now available it was regarded as a waste of labor to draw all of these crystals, only one of which, No. 16,has beenattempted. Figure 3 was drawn to show how various may be the appearance of crystals of stibnite on which identical forms occur but with varying and unequal development of their faces. It is impossible to recognizethe forms except by measurement. In addition to the forms regarded as typical, almost every more complex crystal had single faces to which more or lesSdefinite and simple indices could be assignedbut as they were quite sporadic the data is not presented. It appears that the stibnite crystals from Manhattan may be placed along with those from Felscibanyaand Japan as representing this mineral at the maximum of crystal developmenr.

OnpruBNr Orpiment occurs-.very abundantly at the White Caps Mine, chiefly in massive form or replacing realgar. It was found very rarely in vugs of calcite in the form of isolated crystals. These were in some casesslender needlesof a clear golden yellow color and in others in stout crystals with definite terminations. As is usually the case with this mineral, most of the crystals were bent and bruised but a small number of uninjured crystals was removed and measured. As they add definite proof to that already advanced that orpiment is monoclinic, the data are presented. Furthermore an angle table is given for orpiment, regarded as monoclinic, since none for two-circle measurements has hitherto been printed. The only modern descriptions of orpiment crystals are those of Stevanovicaand Farrington.s Both authors regarded the mineral as monoclinic and gave figures. fn some respectsthe.crystals from Mercur are similar to those here studied. Ten crystals were measured, most of them fragmentary or so intergrown with other individuals that only a part of their faces were accessible. The perfect pinacoidal cleavageand the excellent 372 TH E AM ERICAN MI NERALOGIST development of the prism zone made orientation always definitely possible. In some casesthe measurementswere made by orienting the crystal with (010) as pole. In thesecases only interfacial angles

Frc. 8. Orpiment, Manhattan, Nevada, drawn from back' a

Frc. 9. OrPiment.

were obtained and although these suftced to identify the forms they are not included. in the angles tabulated below' There are three striated zones on the crystals more or less well developed. JOURNAL MINERALOGICAL SOCIETY OF AMERICA J/J

The distinction between thesezones is not easy and it is largely this character that has given rise to the doubt as to whether orpiment is orthorhombic or monoclinic. It was found possibleto distinguish them, however. The prism zone [001] has distinct plane faceswith better lustre and surface than either of the others and striations are not deep. The zoneof positive pyramids [101] and of negative pyramids [101] are similar; both are deeply striated but the signals reflected from the front series[101] were much less numerous than those from the back ones. In addition to these three zonesthe only faces on our crystals were the clinodome l(023) and the positive pyramid i(243). The measurementsobtained were not sufficiently good to permit the calculation of reliable axial elements. The calculated anglesgiven in the following table are therefore basedon the elementsof Stevanovic.

Fonus em c*currrrr o*o *rn"lXXtXl:t"r, onprurwr rnou MAMATTAN ""

No of No of measured rysts. sym- Calculated bol on Limits O in Limits p in .-t- muutes minutes .st6 (010) b 90000, 0o 0' to -33' 6 (100) a 90 00 *:t' 90 20 Oto -42 3 2 (32O) s 68 I 68 o7 +12 to -12 3 2 (r fr 10) 59 12 59 16 +47 to -34 5 4 ( u 120) 39 59 39 49 +26 to -28 I 5 (2s0) 33 51 33 41 +1to-1 2 2 (130) I 29 13 29 +4to-5 6 5 I (023) I JZ zJ 55, (101) 90 00 48 25. 92 40 I 1 e (103) 20 59. d (103) -90 00 19 48 (10r) 47 49 -89 40 47 49 2 q {4e) -58 34 29 33 O12) -73 14 49 03. -76 56 48 52 I -68 6N) 07 49 56. -68 22 *37 to -37 49 57 +16 to - 14 6 -51 (343) 13 54 46 -51 43 +71 to -98 55 08 +72 Lo -99 8 p Q32\ 56 05 )) (s8s) -46 03 56.s3 -46 11 I I (121) -39 4I -39 41 6t 27 'J 1252) -33 34 63 23 -33 59 2 -28 (131) 57 66 19 -32 14 +71 to -70 66 10 +10 to -11 2 *6 (414) 81 37 48 44 82 23 48 56 3 (313) 78 52 48 58 76 56 +13to -17 48 32 +44 to -31 (212) 73 34 49 36 74 16 *39 to -56 49 22 +22 to -58 6 t (243) 40 26 49 21 41 48 50 03 3 k Ozs) -39 04 29 44 fr (i33) -28 25 37 06 z (s23) 76 4l 62 33 (423) -73 t6 57 01

* Indicates new forn, 374 TEE AM ERICAN M INERALOGIST

The elementson which the angleswere calculated are as follows:- aibic:0.5962:1:0.6650. p:90"41' ps:1.1154, 4o:0.6650. /r:89o19' The agreementof calculated and measuredangles is not good but it is at least as good for the forms indicated in the table as new as for those already established.

largest crystal, measuringabout 1 cm. in width and heighth' It was not completely bounded by the prism zone but the prisms found on it have been restored. A further evidence of the monoclinic character of orpiment was

of the five cleavageflakes examined. Brslrocnepuv 1. Ferguson,H. G. The LimestoneOres of Manhattan, Nevada,Ec' Geol''16' 1921,pp. 1-36. z. FergusonfU. G. Geologyand ore Depositsof the Manhattan District, Nevada, .u. S. Geol.Sun. Bull'.,723,1924. 3. Nefi, O. Ueber Antimonit von Ichinokawa (Japan),Bei'lriige zur Kryst',2'VIII' t923, pp. 47-97. 4. Stevanovic,S. Auripigment von Allchar in Macedonien, Zeit' Jiir Kryst'' 39' 1904,14-18. 5. Farrington,O. C. and Tiilotson,E. W. Notes on various Minerals, Orpiment from Mercur, rJtah, Field Colun'bi'anMuseum, GeoI. Series, Vol. III, No. 1, 1905,pP. 154-1.58.