1. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
HZH, Tanta UnivPage1
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
2. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
HZH, Tanta UnivPage2
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)
3. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
HZH, Tanta UnivPage3
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
4. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
HZH, Tanta UnivPage4
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")
5. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
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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)
6. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
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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
7. PRACTICAL PROSPECTOR'S GUIDE TO MINERALS[ ] October 3, 2012
HZH, Tanta UnivPage7
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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HZH, Tanta UnivPage8
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