Mineral Identify, Practical Guide to identify hand specimen mineral in field, very easy,

1. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
PRACTICAL PROSPECTOR'S GUIDE TO
MINERALS
By
Prof. Dr. Hassan Z. Harraz
Geology Department
Faculty Sciences, Tanta University-Egypt
hharraz2006@yahoo.com
Outline
Topic 1:Rock-Forming Minerals
Topic 2:Ores (Metallic)
Topic 3:Ores (NON-Metallic)
Topic 4:Industrial Minerals
Topic 5:Gem Minerals
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2. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
PRACTICAL PROSPECTOR'S GUIDE TO
MINERALS
I- Rock-Forming Minerals
Quartz
 Most common mineral species
 Vitreous luster; conchoidal fracture; hexagonal, prismatic crystals are
diagnostic
 Many color varieties: amethyst, smoky, rose, citrine
 Uses: glass manufacture, abrasive, flux, optical instruments,
electronics
Feldspar Group
Potassium feldspars: microcline, orthoclase, sanidine
 blocky crystals, often show perthitic texture (especially microcline)
Plagioclase feldspars: albite – anorthite series
 range from white to black
 often show play of colors (labradorescence)
 striations on cleavage surface (albite twinning)
Mica Group
Muscovite (white mica)
Biotite (black mica)
Phlogopite (brown mica)
Sericite (brown to buff mica)
Lepidolite (purple mica)
 lithium-rich pegmatites
 micaceous cleavage, elastic nature of plates and hardness distinguish
micas from all other sheet-like minerals such as talc, gypsum and
brucite
Pyroxene Group
 Generally green to black (except spodumene, which can be white,
yellowish, pink or green).
 2 good to perfect cleavages at nearly right angles (chief distinguishing
 characteristic between pyroxenes and amphiboles).
 Pyroxenes are common in mafic to ultramafic rocks and in skarns
 Emerald-green diopside (chrome-diopside) is a diamond indicator
mineral
 Spodumene is a lithium pyroxene found in rare-element pegmatites
 Jadeite is one of the "true" jades and is a pyroxene
Amphibole Group
• Generally green to black (some, like tremolite, are white)
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3. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
 2 good to perfect cleavages at 56 and 124 degrees (chief
distinguishing
 characteristic between amphiboles and pyroxenes).
 BC jade is "nephrite", a variety actinolite, and is considered a "true"
jade.
 amphiboles are common in skarns and in fairly high-grade
metamorphic rocks.
Garnet Group
Almandine (iron – aluminum garnet)
 generally red
 found in schists
Pyrope (magnesium – aluminum garnet)
 generally red
 diamond indicator mineral (kimberlites, lamprophyres)
Spessartine (manganese – aluminum garnet)
 red to orange
 most often in rare-element pegmatites
Grossular (calcium – aluminum garnet)
 brown, green, red, yellow
 often found in skarns
 gem brown variety known as "hessonite"
Andradite (calcium – iron garnet)
 brown, green, red, yellow, black
 often found in skarns
 gem green variety could be "demantoid"
 titaniferous variety (black) is known as "melanite"
Uvarovite (calcium – chromium garnet)
 chrome green
 associated with altered ultramafic rocks.
Serpentine Group
 varied green color, greasy luster, often fibrous (or splintery)
Olivine
 vitreous luster, conchoidal fracture, green color, presence in basalt as
nodules
Carbonate Group
Calcite
 3 cleavages not at right angles
 fizzes readily with weak acid
Siderite
 typical carbonate cleavage
 light to dark brown
Dolomite
 curved, rhombohedral crystals
 white, pink, gray
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4. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
II- Ores (Metallic)
A. Gold
B. Platinum Group Elements:
 Platinum, Palladium, Iridium, Osmium
 placer deposits, ultramafic rocks
C. Native Silver
 wires in pockets, hackly fracture, tarnishes black
 often as an impurity in galena
D. Sulfosalts
 Pyrargyrite/Proustite (ruby silvers)
 Stephanite
 Tetrahedrite
E. Native Copper (100% Cu)
 often in basalt; sometimes in oxidized zone; hackly fracture,
copper color
F. Chalcopyrite (35% Cu)
 no cleavage, greenish-black streak, slightly greener yellow than
pyrite
G. Bornite (63% Cu)
 purple-blue iridescent tarnish, BRONZY on FRESH
SURFACE
H. Covellite (66% Cu)
 ELECTRIC BLUE, platy cleavage
I. Chalcocite (79% Cu)
 black, SECTILE
J. Galena
 3 perfect CLEAVAGES at right angles, DENSITY, lead-gray
color
 secondary lead minerals: anglesite, cerussite, pyromorphite
J. Molybdenite
 chief ore of molybdenum
 SOFT, slightly bluer-gray than graphite (compare it with a
pencil ‘lead’)
L. Pyrite
 often in good crystals (pyritohedra, cubes, octahedra); brittle,
black streak
M. Arsenopyrite
 no cleavage, "garlic" smell sometimes when broken
N. Pyrrhotite
 bronzy color, sometimes magnetic
O. Stibnite
 main ore of antimony.
 elongate crystals that are often ‘bent’; ONE PERFECT
CLEAVAGE and lower density distinguish it from galena.
 will easily melt in a candle flame
P. Graphite
 SOFT, black (like pencil "lead")
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5. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
III- Ores (NON-Metallic)
A. Sphalerite
 resinous to sub-metallic luster
 yellow to green to red to black
 Important ore of cadmium as well
 alters to smithsonite, hydrozincite (fluorescent)
B. Wolframite
 HEAVY, reddish to black, tabular crystals with one perfect
cleavage
C. Scheelite
 White to brown, fluoresces bluish white
D. Manganese Oxides
 psilomelane is a mixture of compact manganese oxides;
mixture of earthy manganese oxides is known as wad.
 black, soft (often show dendritic stains)
E. Iron Oxides
 mixture of iron oxides is generally known as limonite
1. Hematite: red-brown streak
2. Goethite: brown streak
F. Magnetite
 black, dense, MAGNETIC
G. Cassiterite
 black; glassy to resinous luster
H. Cinnabar
 red; bright red streak; soft
I. Cuprite
 red, often associated with malachite or other secondary copper
minerals
J. Malachite/Azurite
 both are alteration products of other copper minerals
 (MALACHITE is GREEN; AZURITE is BLUE (‘azure-blue’,
in fact)
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6. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
IV- Industrial Minerals
Diamond
 as adamantine crystals in kimberlite or lamprophyre
 placer deposits (weathered kimberlites/lamprophyres)
Sulfur
 as a native element in sedimentary rocks (often associated with
petroleum)
Barite
 one to two good cleavages, VERY heavy
 in hydrothermal veins and sedimentary exhalative deposits
Gypsum
 white to gray, softness is characteristic
 sedimentary rocks
Magnesite
 generally white
 found most commonly in sedimentary rocks, but also in
carbonatites
 hydromagnesite and epsomite are evaporites found in playa
lakes (from the alteration of volcanic rocks)
Apatite
 hexagonal crystals, many colors
 found in many environments
 distinguished from beryl by its hardness (beryl cannot be
scratched by a knife)
Zeolite Group
 generally white or off-white
 found in volcanic rocks or low grade metamorphic rocks
 economic deposits found as beds of altered volcanic ash
 "boil" when torched
Fluorite
 four directions of perfect CLEAVAGE
Corundum
 HARDNESS of 9
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7. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
V- Gem Minerals
The following are reasonable to be expected, or have already been found in British
Columbia.
Corundum
 Ruby: red corundum coloured by chromium
 Sapphire: BLUE, green, pink, yellow, colourless corundum coloured
by iron and/or titanium
Diamond
Beryl
 hexagonal cross-section; prismatic to tabular crystals; generally in
pegmatites
Varieties of Beryl:
 Aquamarine: blue to green beryl coloured by iron
 Emerald: green beryl coloured by chromium or vanadium
 Goschenite: colourless beryl (originally cesium-bearing beryl)
 Heliodor: yellow beryl coloured by iron
Tourmaline
 diamond-shape cross-section; perfect basal cleavage (perpendicular to
the length of the crystal)
Varieties of Gemmy Tourmaline:
 Schorl: black tourmaline found in simple pegmatites, hydrothermal
veins and metamorphic rocks
 Elbaite: lithium-bearing tourmaline found almost exclusively in
pegmatites;
 Rubellite (pink), Verdelite (green), Indicolite (blue), Achroite
(colourless)
 Liddicoatite: another lithium-bearing tourmaline, again in pegmatites
Topaz
 diamond-shape cross-section; perfect basal cleavage (perpendicular to
the length of the crystal)
Garnet
 metamorphic rocks; pegmatites
Varieties of Gemmy Garnet:
 Grossular: gem brown variety is hessonite
 Andradite: gem green variety is demantoid
 Spessartine: bright orange is best quality
Quartz
Varieties of Quartz:
 Amethyst: purple quartz coloured by iron (Fe4+)
 Citrine: yellow/orange quartz coloured by iron
 Smoky Quartz: brown to black quartz affected by radiation
 Rose Quartz: pink quartz coloured by manganese
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8. [PRACTICAL PROSPECTOR'S GUIDE TO MINERALS] October 3, 2012
 Chalcedony: cryptocrystalline quartz; gray, greasy to silky luster;
found in volcanic rocks and some sedimentary rocks
 Agate: concentrically banded chalcedony; variously coloured
 Onyx: flat, layered chalcedony; usually black/white or red/white<
 Carnelian: chalcedony coloured red by iron
 Chrysoprase: chalcedony coloured green by nickel
 Jasper: chalcedony coloured red, green, yellow or black by iron oxide
Opal
 in volcanic and sedimentary rocks
 common versus precious opal
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