DOCSLIB.ORG

Crystalline Gold Great New Find

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Crystalline Gold Great New Find MINERALS ISSUE 1 2010 NEWSPAPER FOR COLLECTORS # . o t . o o t h o p l h i p v l o i c Great new find: v o S c . J S . J In this issue: Adelaide Mine 2010 Tomasz PRASZKIER & Adam WRIGHT Collector interview: Jeff Scovil INTRODUCTION The Dundas Ag-Zn-Pb mining field In this first issue of our news- is located about 10 km east of Zeehan, paper, we start a regular column – The Adelaide Mine, located in and contains a number of mines. Two of interviews with well known and Western Tasmania, is undoubtedly the them are especially productive in terms interesting collectors. For our first in - world’s most famous producer of cro - of crocoite specimens – Adelaide and terview – famous photographer and coite specimens. Only a few great pock - Red Lead. The Adelaide mine however, not very well known collector – Jeff ets with top quality specimens have been produces much bigger quantities of high Scovil !! found in the history of the mine – in quality specimens, including occasional 1970’s, 1990’s and then again in 2010! finds of great pockets filled with the Tomasz Praszkier (Minerals): Jeff The “2010 Pocket” produced a number of world’s best crocoite specimens. – You are probably known to min- world-class specimens with great color eral collectors all over the world ... and exceptional crystal size. Crocoites HISTORY OF THE ADELAIDE MINE from this find are surely among the world’s best. Following is the first writ - The deposit mined recently at the Read on page 13 ten account of this recent find. Adelaide mine was discovered in 1887. The most important period of a large- DUNDAS AREA – WORLD PRIME PRO - scale mining for lead and silver took 1st International Mindat.org DUCER OF CROCOITE SPECIMENS place there from 1890-1915. Crocoites Conference in Poland There are two crocoite producing Continued on page 8 11-17 VII 2011 regions in the Western Tasmania, the Heazlewood district, and the Dundas dis - Crocoite from “2010 Pocket”, The First Mindat.org Interna- trict. 10.1 cm high. Gobin specimen. tional Conference will be held in con - junction with the 14th Lwówek Âlàski Crystal Days Festival, three days of mineral shows, events and live music, where the whole town comes out to celebrate the mineralogical heritage of the region. Visitors can enjoy both Crystalline gold the Conference and the Crystal Days festival at the same time. Read on page 7 from Round Mtn, USA R. Scott WERSCHKY INTRODUCTION Is it a collectors dream, or nightmare? It is easy to justify having one good spec - Imagine going to the Tucson Gem imen from the mine, but does one really and Mineral show, and seeing some new need ten pieces just because they are golds from a mine you have never heard all different? This dilemma has many of. They are leafy specimens with bright, mineral collectors, and especially gold shiny, yellow gold and hints of octahedral collectors, scratching their heads and crystals on the edges. The specimens are then digging deep into the pocket books pretty and inexpensive, and you have to all because the Round Mountain mine have one. Then you return to Tucson the went from being an obscure gold locality . o t next year and see more golds from the to being a world class specimen pro - o h p same mine with even better crystals. ducer virtually overnight. l i v Now do this for several years in a row, o c S . finding different crystal habits, bigger HISTORY . o t J and better crystals, better luster, and o h p larger specimens both on and off matrix! Nevada is known as the Silver State, l i v stemming from the famous silver mines Editors: o c S Crystalized gold from Round Mountain of the Comstock Lode discovered in 1859. Tomasz Praszkier (Poland) . J Prospectors bound for the California Scott Werschky (USA) mine. Size 6.8 cm. Spirifer collection. Associated photographer: Jeff Scovil (USA) Contact: www.SpiriferMinerals.com [email protected] 2 CRYSTALLINE GOLD FROM... MINERALS ISSUE 1 # typified by very fine grained dissemi- USA nation and/or supergene enrichments within silicified tuffs. There are probably RRoundound MMountainountain only a few of these specimens in exis - CANADA qquarryuarry tence, likely well hidden by dust on some geologist’s desk. Ottawa Until the early 1990’s, Round Moun - San Francisco tain was considered to be a very low Round Mountain Washington grade deposit that was remarkable only Los Angeles USA in the total lack of visibly interesting M E rock textures or veining. Things forever X IC changed in March of 1992, when coarse Sign at the entrance to the Round Moun - O tain mine. S. Werschky photo. Mexico gold was found in a blast hole. A routine 5 km ore control assay of blast hole cuttings came in at greater than 30 g/t, quite a Toquima Range in central Nevada, Map of North America with location of Round Mountain and aerial view of the open pit divergence from the expected 0.6 g/t. approximately 240 km east-southeast of mine. Assuming there to be some sort of ana - Carson City. It is in the heart of the Basin lytical error, geologists sampled drill cut - and Range Physiographic Province. Mother Lode found placer gold near shut down completely with the onset of tings piled up around the drill hole. For those familiar with the vast deserts what is now Dayton, Nevada. Although WWII. Round Mountain remained more Processing the cuttings with a gold and mountains of the Western United looking for gold, they struck it rich with or less dormant until the late 1960’s pan yielded more than one kilogram of States, it might appear to be in “the mid - silver at Virginia City just a few kilome - when the Ordich Group picked up the coarse grained gold from what turned dle of nowhere ”. For those lovers of crys - ters north of Dayton. This success with claims. The present day Round Mountain out to be the discovery of the first mod - talline gold, it is arguably “the center silver dictated the exploration focus in mine was commissioned in 1977 with ini - ern day high-grade vein. Since this of the Universe” (at least temporarily). tial inferred (not proven) gold reserves discovery, approximately 150 high grade The original town site of Round Moun - of 18.6 metric tones, and a planned mine life of about 6 years. Through a series of mergers and buyouts, the mine is now a 50:50 joint venture between Barrick Gold and Kinross with Kinross acting as operator. The mine has been in continual operation since 1977, with peak gold production of over 22.7 metric tonnes (730,000 ounces) per year. Total produc - tion to date is nearly 373.2 tonnes (12 million ounces) plus the approximately 10.9 tonnes (350,000 ounces) mined before 1977. Current gold reserves are reported at 46.6 metric tonnes at a grade of 0.64 g/t, with an expected mine life of about 3 years. These figures are based on current gold prices, and future changes may extend the mine life espe - cially if they elect to pursue underground mining. At a minimum, total gold pro - duction for the district will be a stagger - Western portion of the Round Mountain pit with heap leach pads in middle distance, ing 435.4 tonnes (14 million ounces) by and Toiyabe Range in far distance. S. Werschky photo. the time it is mined out! Not bad for a mine that started out with hopes of pro - ducing less than 20 tonnes of gold! veins have been encountered. Projection tain still exists, and is adjacent to the Crystalized gold. Size 8 cm. A. Day coll. The first gold specimens found of the high grade vein trend up to the present day open pit mine. Perhaps 40 J. Scovil photo. during modern mining operations were pre-mining surface on Stebbins Hill cor - people still live there, although the min - relates with veins worked during early ing company is trying to convince them Nevada for the next 40 years. The sub - mining around 1910. Historical research to relocate in order to expand the open sequent decline of the mines of the Com - showed that coarse gold was indeed pit mine to the northeast which would stock lead to renewed exploration efforts known back then as evidenced by photos consume the town. Most of the miners which resulted in several major gold of large gold specimens displayed during live in the small town of Carvers or the rushes in Nevada starting around 1900. a gold mining conference in Chicago, Illi - company sponsored housing in what is Many famous gold mines were found at nois circa 1909. known as the Hadley Subdivision. this time, including Round Mountain It is estimated that more than 9330 which was discovered by Louis Gordon kg (300,000 ounces) of coarse gold have in 1906. In a very short time, there were been recovered since 1992. Unfortu - thousands of miners living in tents and nately, no records exist for historic pro - primitive wooden shacks. At the peak, duction of specimen-grade gold. Round Mountain was producing a lot of 36 kg pile of gold from the high grade After the discovery of the high grade vein! Photo taken ca. 1992 by B. Veek. gold each year, especially considering vein in 1992, geologists at the mine con - the labor intensive mining methods of vinced management to initiate a sales the era. The district produced more than encountered around 1980 in the densely program in which all employees could 300 kg (10,000 troy ounces) of gold a welded tuffs at the top of the caldera buy a few pieces of gold at the prevailing year during early years.
Load more

Recommended publications
  • C:\Documents and Settings\Alan Smithee\My Documents\MOTM
    Itkx1//7Lhmdq`knesgdLnmsg9Rshbgshsd Our ongoing search for new minerals to feature finds us scouring the more than forty separate shows that comprise the Tucson Gem & Mineral show every year, looking for large lots of interesting and attractive minerals. The search is rewarded when we make a new contact and find something especially vibrant like this month’s combination of lavender stichtite in green serpentinite! OGXRHB@K OQNODQSHDR Chemistry: Mg6Cr2(CO3)(OH)16A4H2O Basic Hydrous Magnesium Chromium Carbonate (Hydrous Magnesium Chromium Carbonate Hydroxide) Class: Carbonates Subclass: Carbonates with hydroxyl or halogen radicals Group: Hydrotalcite Crystal System: Trigonal Crystal Habits: Crystals rarely macroscopic; usually as crust-like aggregates in matrix; sometimes radiating, micaceous with flexible plates, and nodular with tuberous, irregular surface projections; also massive and fibrous. Color: Lavender, lilac, light violet, pink, or purplish. Luster: Waxy, greasy, sometimes pearly. Transparency: Transparent to translucent Streak: White to pale lilac Refractive Index: 1.516-1.542 Cleavage: Perfect in one direction Fracture: Uneven, brittle. Hardness: 1.5-2.0 Specific Gravity: 2.2 Luminescence: None Distinctive Features and Tests: Softness, color, crystal habits, occurrence in chromium-rich metamorphic environments, and frequent association with serpentinite (a greenish metamorphic rock). Stichtite can be confused with similarly colored sugilite [potassium sodium iron manganese aluminum lithium silicate, KNa2(Fe,Mn,Al)2Li2Si12O30].
    [Show full text]
  • CROCOITE Margaret Woodward
    CROCOITE Margaret Woodward A rock board, a rock pick and the philosopher’s stone. In the presence of all that is absent, these are the objects with which this search begins. 1 CROCOITE Prologue H was always attracted to the ‘ologies’. Geology, archaeology, minerology. She found these words in the museum and on the bookshelf, to be quite thrilling. For her eleventh birthday she asked for a geologist’s pick so that she could go crystal hunting, fossicking, prospecting. She’d seen one in the local hardware store, under a thick glass-topped counter and knew that this was going to be the tool for her to navigate the world. She held the weighty gravity of it, felt its pull towards the earth’s crust and registered instinctively the promise that it held. This was her opportunity to really know the world. Her father had a rock collection himself, kept in a box that might have once held cigars or chocolate. Its wooden dividers carefully walling the world. She too wanted to fill that box with precious specimens, to sit each one on a small mattress of cotton wool, to fill its compartments with his pride in her discoveries and keep the absences at bay. With her rock pick she dug and pried, punctured, dragged and sifted the earth’s crust through her fingers, felt its texture and grit. Chip chipping away at crystals on east coast granite, the rock pick ricocheting crazily off boulders, and jarring her wrists and hands. She spent her childhood sorting and classifying the world into her own muse-eology.
    [Show full text]
  • A Mineralogical Field Guide for a Western Tasmania Minerals and Museums Tour
    MINERAL RESOURCES TASMANIA Tasmania DEPARTMENTof INFRASTRUCTURE, ENERGY and RESOURCES Tasmanian Geological Survey Record 2001/08 A mineralogical field guide for a Western Tasmania minerals and museums tour by R. S. Bottrill This guide was originally produced for a seven day excursion held as part of the International Minerals and Museums Conference Number 4 in December 2000. The excursion was centred on the remote and scenically spectacular mineral-rich region of northwestern Tasmania, and left from Devonport. The tour began with a trip to the Cradle Mountain National Park, then took in visits to various mines and mineral localities (including the Dundas, Mt Bischoff, Kara and Lord Brassey mines), the West Coast Pioneers Memorial Museum at Zeehan and a cruise on the Gordon River. A surface tour of the copper deposit at Mt Lyell followed before the tour moved towards Hobart. The last day was spent looking at mineral sites in and around Hobart. Although some of the sites are not accessible to the general public, this report should provide a guide for anyone wishing to include mineral sites in a tour of Tasmania. CONTENTS Tasmania— general information Natural history and climate ………………………………………………… 2 Personal requirements ……………………………………………………… 2 General geology…………………………………………………………… 2 Mining history …………………………………………………………… 4 Fossicking areas — general information ………………………………………… 4 Mineral locations Moina quarry …………………………………………………………… 6 Middlesex Plains ………………………………………………………… 6 Lord Brassey mine ………………………………………………………… 6 Mt Bischoff ………………………………………………………………
    [Show full text]
  • Stratiform Chromite Deposit Model
    Stratiform Chromite Deposit Model Chapter E of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–E U.S. Department of the Interior U.S. Geological Survey COVER: Photograph showing outcropping of the Bushveld LG6 chromitite seam. Photograph courtesy of Klaus J. Schulz, U.S. Geological Survey. Stratiform Chromite Deposit Model By Ruth F. Schulte, Ryan D. Taylor, Nadine M. Piatak, and Robert R. Seal II Chapter E of Mineral Deposit Model for Resource Assessment Scientific Investigations Report 2010–5070–E U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Schulte, R.F., Taylor, R.D., Piatak, N.M., and Seal, R.R., II, 2012, Stratiform chromite deposit model, chap. E of Mineral deposit models for resource assessment: U.S.
    [Show full text]
  • The Chemistry of Chromium and Some Resulting Analytical Problems by Saul 1
    Environmental Health Perspectives Vol. 92, pp. 7-11, 1991 The Chemistry of Chromium and Some Resulting Analytical Problems by Saul 1. Shupack* Chromium, named for its many-colored compounds, exists in the oxidation states of -2 to +6 inclusively. The compounds exhibit a wide range ofgeometries including square planar, tetrahe- dral, octahedral, and various distorted geometries. Chromium is found in nature principally as the chromite ore FeCr2O4 in which chromium is in the +3 state. The existence of a particular oxidation state is dependent on many factors including pH, redox potentials, and kinetics. Thermodynamically, +3 and +2 are the most stable states, while the +3 and +6 oxidation states are the most common ones found in aqueous solution. Kinetically, chromium +3 is substitution- ally inert: for water exchange k(sec-') = 2.5 x 10, due to the presence of the half-filled d(tg,)34A2 state. On the other hand, protonation/deprotonation is quite rapid. Polymerization is very slow but is promoted at higher pHs; acid cleavage of the protonated oligomers is also quite slow. Chromium +6 as the chromate ion is strongly oxidizing at low pHs and less so in basic solution. The chromate ion does form some polyacids and polyanions. These factors must be considered in analyzing samples for total chromium and for the amounts of each oxidation state. General Chromium was named for the many colors manifested by its compounds. As is seen in Figure 1, potassium dichromate, K2Cr2O7, is red, potassium chromate, K2CrO4, is yellow, and chromium trichloride, CrCl3, is green. The element (1) is found in the combined form mainly as the chromite ore, FeCr2O4, a spinel.
    [Show full text]
  • Embreyite, a New Mineral from Berezov, Siberia
    MINERALOGICAL MAGAZINE, SEPTEMBER 1972, VOL. 38, PP. 790-3 Embreyite, a new mineral from Berezov, Siberia S. A. WILLIAMS1 British Museum (Natural History), Cromwell Road, London S.W. 7 SUMMARY. Embreyite is a new mineral that has been found only in old specimens collected at Berezov, Siberia. The composition is Pb..9,(CrO.)..oo(PO.)1091.0.75H.O, or Pb5(CrO.).(PO.)..H.O based on both wet and electron-probe analyses. Z = I, Dme" 6.45, Deale 6.41. Crystals are monoclinic with a 9.755 A, b 5.636, c 7.135, f3 103°5'; the space group may be P21/m. No single crystals were found. y a = 2.20, f3 = = 2.36. Colour in various shades of orange with a yellow streak. H = 3t; no cleavages observed. Occurs with vauquelinite, crocoite, and phoenicochroite in the oxide zone assemblage from Berezov. EMBREYITE was first noted on a specimen loaned by J. Jago in 1963. His specimen contained just enough material for a powder spindle, however, so it was not until I obtained additional material that this description could be completed. A fine speci- men, rich in embreyite, was given me by Dr. Sainfeld at the Bureau des Recherches Geologiques et Minieres, and I recently had the opportunity to carefully examine all of the Beresov specimens at the British Museum (Natural History), where a con- siderable amount of embreyite turned up. There are at least two specimens at the B.R.G.M., twelve at the British Museum2 (Natural History), and the original Jago specimen. These specimens comprise an estimated 10 grams of embreyite, and doubt- less there are many other pieces in collections of Berezov material.
    [Show full text]
  • Tasmanian Crocoite
    TASMANIAN CROCOITE Few minerals command as much instant, visual recognition as crocoite. With their bright, orange-red color and complex clusters of elongated, needle-like prisms, it’s no wonder that distinctive and eye-catching crocoite is a favorite among collectors and museum curators. Crocoite is one of only 25 chromate minerals, all of which are rare. Of these, crocoite is the most common and familiar to collectors. Although crocoite has numerous occurrences, there are very few localities that produce fine specimens. The classic crocoite locality is the Zeehan Mining District in Tasmania, Australia. No other source approaches Zeehan when it comes to the color, size, and crystal complexity of crocoite specimens. And the story behind Tasmanian crocoite is as fascinating as the specimens. Crocoite, pronounced CROAK-eh-ite, is the mineral form of lead chromate. Its chemical formula PbCrO4 identifies its elemental components as lead, chromium, and oxygen. Lead comprises 64.11 percent of crocoite’s molecular weight, chromium 16.09 percent, and oxygen 19.80 percent. Crocoite crystallizes in the monoclinic system as elongated, thin, needle-like prisms with generally square cross sections and lengthwise striations. Crocoite crystals typically form reticulated aggregates, acicular (“jackstraw”) clusters, radial sprays, and intricate, random groupings. Crystals are often partially hollow with poorly developed, uneven, or pitted terminations. Crocoite also occurs in granular, columnar, and incrusting forms. Crocoite is translucent to transparent, with a Mohs hardness of 2.5-3.0, an adamantine luster, conchoidal to uneven fracture, distinct cleavage in one direction, and a yellow-orange streak. With a specific gravity of 5.9-6.1, crocoite is among the densest of all translucent minerals.
    [Show full text]
  • Geological Survey Report on the Dundas Mineral Field
    6 9\ 18 GEOLOGICAL SURVEY REPORT ON THE DUNDAS MINERAL FIELD SUMMARY A statement in brief of the practical consideration arising from the survey of the Geologic relations and of the various kinds of ore-bodies should prove acceptable and helpful to the prospector. This account of the results so obtained presents in condensed form the salient features of the discussion that follows. The nature of the rocks and their relation are favourable to ore deposition in some parts, but not in others where the conditions are different. This fact empPasises the necessity for. close attention to detail in the work of Geologic interpretation. The rocks will be dealt with in the order of their formation beginning with the pre-Cambrian. These are schists, almost barren of minerals, occupying a small area fronting Mt. Dundas. The next succeeding formation consists of Cambro-Ordovician sediments and tuffs of the Dundas and Bischoff series which occupy the greater part of the district. No ore deposits of any considerable extent have been found in the Dundas series of rocks except where they are intruded by gabbro, serpentine or quartz and felspar porphyries. The Bischoff series of rocks on the other hand are the repositories or hosts of nearly all the lodes. The reason of this is not difficult of explanation. Pre-Cambrian schists and the sediments and tuffs of the Dundas series are comparatively plastic rocks incompetent to withstand compressive and tensional forces, while the hard quartzite, sandstone and slates of the Bischoff series are strongly resistant rocks and fracture under great strain providing channels of access for mineralising solutions.
    [Show full text]
  • CROCOITE Margaret Woodward
    CROCOITE Margaret Woodward LOST ROCKS CROCOITE Margaret Woodward A rock board, a rock pick and the philosopher’s stone. In the presence of all that is absent, these are the objects with which this search begins. 1 CROCOITE Prologue H was always attracted to the ‘ologies’. Geology, archaeology, minerology. She found these words in the museum and on the bookshelf, to be quite thrilling. For her eleventh birthday she asked for a geologist’s pick so that she could go crystal hunting, fossicking, prospecting. She’d seen one in the local hardware store, under a thick glass-topped counter and knew that this was going to be the tool for her to navigate the world. She held the weighty gravity of it, felt its pull towards the earth’s crust and registered instinctively the promise that it held. This was her opportunity to really know the world. Her father had a rock collection himself, kept in a box that might have once held cigars or chocolate. Its wooden dividers carefully walling the world. She too wanted to fill that box with precious specimens, to sit each one on a small mattress of cotton wool, to fill its compartments with his pride in her discoveries and keep the absences at bay. With her rock pick she dug and pried, punctured, dragged and sifted the earth’s crust through her fingers, felt its texture and grit. Chip chipping away at crystals on east coast granite, the rock pick ricocheting crazily off boulders, and jarring her wrists and hands. She spent her childhood sorting and classifying the world into her own muse-eology.
    [Show full text]
  • The Distribution and Occurrence of Zeolites in Tasmania
    The Distribution and Occurrence of Zeolites in Tasmania Steve Sorrell April, 2003 The Distribution and Occurrence of Zeolites in Tasmania 1. Introduction Zeolites are a large group of minerals exhibiting similar general characteristics and properties. Characteristics of zeolites include the potential for low-temperature dehydration, and the ability to readily absorb other molecules, resulting in zeolites being utilised in industrial activities. The International Mineralogical Association Commission on New Minerals and Mineral Names have recently published a report that redefines the nomenclature for zeolite minerals (Coombs et al, 1997). This redefinition has resulted in around 90 mineral species being included within the zeolite group, a significant increase. In some cases, it has also caused some difficulty for collectors in naming their specimens, particularly the revised approach to what are now referred to as “compositional series” (eg: chabazite series now contains chabazite-Ca, chabazite-Na, etc, based on the dominant cation). The difficulty arises from the need to chemically test specimens (XRD is insufficient), and the fact that a range of “species” may occur in the one location, perhaps even on one specimen. Limited testing of Tasmanian zeolites has been carried out. In Tasmania, some 27 species of zeolites have been recorded. This publication is aimed at beginners and serious collectors of Tasmanian zeolites and contains a comprehensive report of all known localities and the species recorded from each. Photographs have been included wherever possible to aid in the identification of specimens found by collectors. Some sites are worked out or otherwise off-limits to collectors. Where this information is known, it is included in the text.
    [Show full text]
  • Occurrences of Gemstone Minerals in Tasmania
    Occurrences of Gemstone Minerals in Tasmania Department of State Growth Mineral Resources Tasmania Occurrences of Gemstone Minerals in Tasmania (8th edition 2nd printing) Compiled by R. S. Bottrill and W. L. Matthews 1st Print April 2006 2nd Print November 2019 Mineral Resources Tasmania PO Box 56 Rosny Park Tasmania 7018 www.mrt.tas.gov.au ISBN 0 7246 4011 8 While every care has been taken in the preparation of this book, no warranty is given as to the correctness of the information and no liability is accepted for any statement or opinion or for any error or omission. No reader should act or fail to act on the basis of any material contained herein. Readers should consult professional advisers. As a result the Crown in Right of the State of Tasmania and its employees, contractors and agents expressly disclaim all and any liability (including all liability from or attributable to any negligent or wrongful act or omission) to any persons whatsoever in respect of anything done or omitted to be done by any such person in reliance whether in whole or in part upon any of the material in this book. Introduction This book has been prepared as a guide for people who are interested in collecting and polishing Tasmanian gemstones and is an updated version of the seventh edition compiled by W. L. Matthews and R. S. Bottrill in 1993. The descriptions and localities of the various minerals have been compiled from a number of sources. These include: Catalogue of the Minerals of Tasmania by W. F. Petterd, 1910 (a revised edition was issued as Geological Survey Record 9, 1970); Lancaster (1980, 2000); Gemstones in Tasmania by P.
    [Show full text]
  • Properties of Minerals Crystal Habits Cleavage and Fracture in Minerals
    1 Some of the samples used in Mineralogy Lab are museum specimens. Please do not destroy them. You can do just about anything you want to the grungy ones, but be nice to the pretty specimens as they are irreplaceable. Name______________________________ Properties of Minerals Crystal Habits Not all mineralogical samples form nicely shaped crystals but, when they do, the shape can be helpful in identifying the mineral. The habit of a crystal refers to its shape. (But, it refers only to the shape that the crystal forms as it grows, not as it breaks--see next section of cleavage and fracture.) For example, some minerals such as halite tend to be cubic, while others such as the micas are foliated and tend to form sheets or books. A large number of terms are used to describe habit; they are summarized in your mineralogy text (Table 3.2). Some of the most commonly used terms that you should be familiar with are: equant dendritic bladed granular blocky massive tabular concentric columnar prismatic foliated cubic micaceous hexagonal sheety octahedral fibrous orthorhombic Make up your own terms if you want to, just as long as they have a clear meaning (e.g., "grape-like"). Cleavage and Fracture in Minerals Cleavage, parting and fracture refer to the ways a mineral breaks when an external force is applied. Since minerals have atomic structures that are not the same in all directions, there are some preferred directions and methods of breaking. Cleavage is the tendency of minerals to break along one or more sets of parallel plains.
    [Show full text]