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GY 302: Crystallography &
Mineralogy
GY 302: Crystallography &
Mineralogy
UNIVERSITY OF SOUTH ALABAMA
Lecture 8: Native ElementsLecture 8: Native Elements
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Last Time
1. Mineral properties under XN (crossed Nichols/polars)
2. Mineral Classes/Properties
3. Native Elements; Chemistry & Crystallography(properties)
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B: Crossed Nichols (XN)
6) Extinction: occurs when the indicatrix aligns up with the
polars and the entire crystal goes black (extinct).
PPLPPL XNXN
Optical Properties
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B: Crossed Nichols (XN)
7) Birefringence. This is the most important property of minerals
under crossed polars. It is defined as the difference between the
index of refraction of the minimum and maximum refractive
indices of a mineral.
For uniaxial minerals; no ne orne - no.For biaxial crystals; n
a
nc
ornc
- na
.
As far as you are concerned, you see pretty colours under XN
Optical Properties
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Optical Properties
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B: Crossed Nichols (XN)
8) Optical Twinning. Same thing as physical twins whereby two
or more crystals of a single mineral grow together in a
mathematically predicable pattern (involves twin planes, twin
axes etc).
Optical Properties
PPL XN
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B: Crossed Nichols (XN)
9) Zonation. Some minerals change their composition has they
grow, particularly those that that form continuous series through
solid solution during igneous processes (e.g., olivine,
plagioclase). This can result in optical zonation.
PPLPPL XNXN
Optical Properties
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Todays Agenda
Native elements1. Chemistry and Crystallography (properties)
2. Occurrences and Associations
3. Economics (resources, reserves, extraction)
Featured Minerals: Gold and Diamonds
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Todays Agenda
Native elements1. Mineral Classes/Properties
2. Chemistry and Crystallography (properties)
3. Occurrences and Associations
4. Economics (resources, reserves, extraction)
Featured minerals: Gold, Diamonds
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Native Elements
Copper Cu Isometric
Gold Au* Isometric
Silver Ag* Isometric
Platinum Pt* Isometric
Arsenic As HexagonalAntimony Sb Hexagonal
Bismuth Bi Hexagonal
Tellurium Te Trigonal
Sulfur S Orthorhombic
Graphite C* Hexagonal
Diamond C* Isometric
Metals
Semi-metals
Non-metals
* primary production from native elements
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Metallic Native Elements
Gold (Au)Crystal: IsometricPt. Group: 4/m32/m
Habit: octahedral, dendritic
SG: 15.6-19.3 (depending on Ag content)H: 2.5-3*
L: metallic
Col: gold-yellow
Str: gold-yellowClev: none
Optical: Opaque
Name Derivation: Anglo Saxon, of uncertain origin.
http://www.rocksandgems.info
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Metallic Native Elements
Gold (Au)Occurrence: quartz veins (igneousrocks, hydrothermal), placer deposits
Associated Mins: quartz, pyrite,
chalcopyrite, galena, stibnite,sphalerite, arsenopyrite, tourmaline,
molybdenite
Related Mins: Calaverite [AuTe2],sylvanite [(Au,Ag)Te2], maldonite[Au2Bi], electrum [Au-Ag solid solution]
http://www.usagold.com/
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Metallic Native ElementsGold (production, reserves in tonnes*)
Production: refined metal produced per year (metric tons)
*1 metric ton (tonne) = 1000 kg = 32,150.7 troy ounces
http://minerals.usgs.gov/minerals/pubs/mcs/2011/mcs2011.pdf
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Metallic Native ElementsResources: a concentration of a material useful to humanity (water, food, minerals)
Geological Resources: all materials (mineral and energy) including those only
surmised to exist, that have present or anticipated future value and which can be
extracted from the Earth via economically feasible methods ($$$) (i.e., gold,
diamonds, coal, oil, natural gas, water)
Reserve Base: The in-place demonstrated (measured+indicated) amount of a
resource that can be extracted via current mining and production techniques
(currently economical + marginal +/- subeconomical) . Equivalent to the old
geological reserve definition.
Reserve (current): That part of the reserve base that could be economically extracted
today
Production: refined metal produced per year (metric tons)
(see lecture suppliments for additional resources jargon)
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Metallic Native Elements
Gold (US data)
2011 Mineral Commodity Summaries. USGS
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Metallic Native Elements
Silver (Ag)Crystal: IsometricPt. Group: 4/m32/m
Habit: massive, acicular
SG: 10.1-10.5H: 2.5-3
L: metallic
Col: silver-white
Str: gold-yellowClev: none
Optical: Opaque
Name: Derivation: Anglo Saxon, of uncertain origin.
http://webmineral.com/specimens/picshow.php?id=1060
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Metallic Native Elements
Silver (Ag)Occurrence: hydrothermal depositsand in oxidized zones of ore deposits.
Associated Mins: arsenopyrite, Ni
and As ores.
Related Mins: dyscrasite [Ag3Sb],
argentite [Ag2S], proustite
[Ag3AsS3], pyrargyrite [Ag3SbS3],amalgram [Hg-Ag solid solution];electrum [Au-Ag solid solution]
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Metallic Native Elements
Platinum Group (Pt, Ir, Pa, Rh, Ru, Os,)
Crystal: IsometricPt. Group: 4/m32/m
Habit: massive, acicular
SG: 21.47H: 4-4.5
L: metallic
Col: gray-silver
Str: gray-silverClev: none
Optical: opaque
Name Derivation: Spanish, platina = "silver."
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Metallic Native Elements
Platinum GroupOccurrence: ultramafic rocks and in
placer deposits.
Associated Mins: chromite, spinel
and olivine
Related Mins: none
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Metallic Native Elements
Platinum Group (US data)
2011 Mineral Commodity Summaries. USGS
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Non-metallic Native Elements
Graphite (C)Crystal: HexagonalPt. Group: 6/m 2/m 2/m
Habit: platey, massive
SG: 2.1-2.2H: 1-2
L: submetallic
Col: lead-gray, black
Str: blackClev: perfect basal {001}
Optical: opaque
Name derivation: From the Greek, graphein, "to write
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Non-metallic Native Elements
Graphite (C)Occurrence: metamorphic rocks (esp.schists, marbles and gneisses). Rare
in igneous rocks.
Associated Mins: none to speak of
Related Mins: none
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Non-metallic Native Elements
Diamond (C)Crystal: IsometricPt. Group: 4/m32/m
Habit: octahedral, twinned
SG: 3.5H: 10
L: adamantine
Col: colorless, rare blue, red,
yellowStr: n/a
Optical: isotropic, n=2.419
Clev: perfect {111}
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Non-metallic Native Elements
Diamond (C)Occurrence: altered ultramafic rocksand carbonated igneous rocks
(Kimberlites)
Associated Mins: olivine, pyrope,zircon, kyanite
Related Mins: none
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Metallic Native Elements
Diamond (production, reserves in 1000s of karats of gem quality stone)
2011 Mineral Commodity Summaries. USGS
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Non-metallic Native Elements
Gemstones (US data)
2008 Mineral Commodity Summaries. USGS
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Emplacement and Extraction
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GoldGold is largely produced through hydrothermal precipitation
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GoldGold is largely produced through hydrothermal precipitation
http://www.chesapeakegold.com/images/maps/hydrothermal-2-full.gif
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GoldGold is largely produced through hydrothermal precipitation
http://gsc.nrcan.gc.ca/mindep/synth_dep/gold/vms/pdf/deposit_synthesis.gold_vms.dube.pdf
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GoldAustralian Gold Deposits
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Gold
Hemlo Gold
play
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Gold
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Gold
Golden Giant Mine (Newmont)
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Gold
Golden Giant Mine
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Gold
Golden Giant Mine
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Gold Extraction
Golden Giant Mine
A typical
underground mine
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Gold Extraction
Waihi open pit gold mine (Newmont),
New Zealand
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Gold Extraction
Summitville (Co) Gold Mine
An atypical open
pit mine
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Gold Extraction
Cyanide Leeching Method
4Au + 8CN- + O2 + 2H2O = 4Au(CN)2- + 4OH-
http://www.daa.com.au/uploads/RTEmagicC_mm_leachfeed.jpg.jpg
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Gold ExtractionHeap Cyanide
LeechingMethod
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Diamonds
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Diamonds
http://members.tm.net/lapointe/Carbon_Phase_Diagram.gif
Diamond
Phase diagram
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Diamond
Kimberlite Pipes
http://www.kimcordiamonds.com/formation.php
http://www.earth.ox.ac.uk/~oesis/field/medium/kimberlite.jpg
Diamonds
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Diamond
Kimberlite Pipes
http://www.kimcordiamonds.com/formation.php
http://gsc.nrcan.gc.ca/diamonds/kirkland/images/c14_3.jpg
Diamonds
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Diamonds
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Diamonds
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Diamonds
Etaki Mine
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Diamonds
http://gsc.nrcan.gc.ca/mindep/synth_prov/slave/pdf/regional_synthesis.slave.bleeker.pdf
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Diamonds
http://gsc.nrcan.gc.ca/mindep/synth_prov/slave/pdf/regional_synthesis.slave.bleeker.pdf
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Todays Homework
1.1. Finish Lab Assignment 5 (Optical mineralogy)Finish Lab Assignment 5 (Optical mineralogy)
Next Lecture1. The Sulfides part 1