Mineral list 1-2

Question 1

Copper

Answer 1

Copper

Reddish brown
Jagged fracture
Hardness 3.0

Associated with basaltic lavas where deposition resulted from the reaction of hydrothermal solutions with iron oxides

For electrical purposes - mostly wire
Conduct heat and electricity very well

Question 2

Sulphur

Answer 2

S

brittle
Conchoidal fracture
resinous luster
2.5 hardness

Occurs near crater rim of active or extinct volcanos
May furnish from sublimation of hydrogen sulfide gas

Used to make sulfuric acid

Question 3

Graphite

Answer 3

C

brittle
Greasy
metallic luster
low specific gravity
<2.5 hardness

occurs in metamorphic rocks such as recrystallized limestone, schists and gneiss.
Metamorphosed coal beds may be partially converted to graphite

Mixed with fine clay to make “lead” for pencils
Mixed with oil for lubricant
Excellent conductor for heat and electricity

Question 4

Chalcocite

Answer 4

CuS2

Very dark rock
hardness 3.0
grey black streak

Occurs as a supergene mineral in enriched zones of sulfide deposits
Occurs in veins associated with pyrite, bornite and chalcopyrite

Primary copper ore

Question 5

Bornite

Answer 5

Cu5FeS4

brownish to bronze on fresh fracture but quickly turns to blue or purple
lighter than covellite
3.0 hardness

occurs disseminated in basic rocks, contact metamorphic rocks, replacement deposits and pegmatites

Ore of copper

Question 6

Galena

Answer 6

PbS

Cubic at 90 degrees
Bright metallic luster
High specific gravity
Soft
hardness 2.0

Found in veins, hydrothermal vents, and replacement bodies in limestone
Found in contact metamorphic deposits, pegmatites, and disseminations in sedimentary rocks

Source of lead

Question 7

Sphalerite

Answer 7

(Fe)ZnS

Sub metallic
Yellow brown streak
Common yellow brown to black - darkening with increase of iron

Found in veins of igneous rocks
Commonly found with galena

Main ore of zinc

Question 8

Chalcopyrite

Answer 8

CuFeS2

Metallic luster
Brass yellow color
greenish black streak
4.0 hardness

Occurs as original constituent in igneous rocks, pegmatite dikes, contact metamorphic rock deposits and disseminated in schistose rock

Important ore of copper

Question 9

Covellite

Answer 9

CuS

Highish specific gravity
Indigo blue or darker
Iridescent
Metallic luster
2.0 hardness

Found in most copper deposits as a supergene mineral - usually as a coating

Minor copper ore

Question 10

Pyrrhotite

Answer 10

FeS

Brownish bronze on fracture
Silver grey elsewhere
4.0 hardness
uneven fracture

Commonly associated with basic igneous rocks - especially norites - where it is disseminated
Found in contact metamorphic deposits, in vein deposits, and pegmatite

Mined for it’s associated nickel, copper and platinum

Question 11

Niccolite

Answer 11

Niccoline

NiAs

Color – pale copper red to gray blackish
Brownish black streak
Higher specific gravity
5.0 hardness
Uneven fracture

Found in vein deposits with cobalt and silver minerals

Minor ore of nickel

Question 12

Cinnabar

Answer 12

HgS

Vermillion red color
Scarlet streak
High specific gravity
2.0-2.5 hardness

Occurs as impregnations and as veins filling near recent volcanic rocks and hot springs
From solutions which were probably alkaline

Ore of mercury

Question 13

Pyrite

Answer 13

FeS2

Conchoidal fracture
Pale brass yellow
Metallic luster, splendent
Greenish or brownish – black streak
Hardness 6.0
Distinguished from chalcopyrite by its paler color

Forms at high and low temperatures but largest masses occur at higher temperature
Forms during the metamorphism of certain rock types, such as shales or sedimentary rocks
Can be found in some igneous rocks, particularly in ore deposits associated with volcanic or hydrothermal activity

Can be used as gemstone
Mined for associated gold, copper
Also mined for the sulfur

Question 14

Marcastie

Answer 14

FeS2

Metallic luster
Pale bronze to almost white
Paler than pyrite
6.0 Hardness

Lower temperature stability range than pyrite which may occur in magmatic segregations
Deposited at low temps from acidic solutions and commonly found under surface conditions as supergene mineral

Source of sulfur
Gemstone

Question 15

Arsenopyrite

Answer 15

FeAsS

High specific density
Metallic luster
Silver white color
Black streak

Occurs with tin and tungsten in high temp hydrothermal deposits

Principal source of arsenic

Question 16

Molybdenite

Answer 16

MoS2

Greasy feel
Metallic luster
Lead blue grey color
Greenish streak
2.0 hardness

Occurs as accessory mineral in certain granites, pegmatites and associated with porphyry copper deposits
Commonly found in high temp deposits and contact metamorphic deposits

Principal source of Molybdenum

Question 17

Pentlandite

Answer 17

(Fe, Ni)9S8

Yellow bronze to black color
Conchoidal fracture
5.0 Hardness
Darker rock than chalcopyrite

Occurs in some mafic or ultramafic intrusive igneous rocks
Formed during the cooling of a sulfide melt

Principal source of Nickel

Question 18

Realgar

Answer 18

As4S4

Resinous luster
Sectile
2.0 hardness
Red orange color

Found in hydrothermal vein deposits
Volcanic sublimation product and deposit from hot springs

Used for pigment and for fireworks but not anymore due to toxicity

Question 19

Orpiment

Answer 19

As2S3

Lemon yellow color - paler than realgar
Pale yellow streak
Sectile
2.0 Hardness

Found in hydrothermal vein deposits
Volcanic sublimation product and deposit from hot springs

Used for pigment and in fireworks - not anymore

Question 20

Stibnite

Answer 20

Sb2S3

Shows parallel striations
Metallic luster
Lead grey to black streak
Uneven fracture
Metallic silvery-gray to a lead-gray color

Found in low temp hydrothermal veins or replacement deposits

Primary ore of Antimony

Question 21

Skutterudite

Answer 21

CoAs3

Metallic luster
Tin-white to silver-gray
Black streak
6.0 hardness
uneven fracture

Found with cobaltite and nickeline in veins formed at moderate temperatures
Commonly associated with silver, arsenopyrite and calcite

Ore of cobalt and nickel

Question 22

Enargite

Answer 22

Cu3AsS4

Metallic luster
Grayish black to iron black color and streak
3.0 hardness

Rare mineral found in vein and replacement deposits formed at moderate temps associated with pyrite, galena and covellite

Ore of copper

Question 23

Freibergite

Answer 23

Tetrahedrite but with more silver (argentiferous)

(Cu, Fe, Zn, Ag)12(Sb, As)4S13

Metallic gray to black color
Reddish to black streak
3.5 - 4.0 hardness
Metallic luster
Darker than tetrahedrite

Forms in hydrothermal vein deposits
Deposits can occur in sedimentary, metamorphic and igneous host rocks

Silver ore

Question 24

Tetrahedrite

Answer 24

(Cu, Fe, Zn, Ag)12(Sb, As)4S13

Metallic gray to black color
Reddish to black streak
3.5 - 4.0 hardness
Metallic luster

Forms in hydrothermal vein deposits
Deposits can occur in sedimentary, metamorphic and igneous host rocks

Ore of copper and silver

Question 25

Cuprite

Answer 25

Cu2O

Conchoidal fracture
Ruby red to green
Lighter colored rock
3.5 hardness
Metallic luster

Supergene copper mineral found in upper oxidized portions of copper veins

Minor ore of copper

Question 26

Zincite

Answer 26

ZnO

Sub adamantine luster
Deep red to orange yellow color
Black crystals
Orange-yellow streak
Higher specific gravity
4.0 hardness

Confined to zinc deposits at Franklin and Sterling Hill
Associated with franklinite and willemite in calcite

Ore of zinc

Question 27

Magnetite

Answer 27

Fe3O4

Metallic luster
Magnetic
Iron black color
High specific gravity
6.0 hardness
Uneven fracture

Occurs as thin plates and dendric growths between plates of mica
May form large ore bodies through magnetic segregation
Disseminated as an accessory through most igneous rocks

Important iron ore

Question 28

Franklinite

Answer 28

(Zn, Fe, Mn)(Fe, Mn)2O4

Metallic luster
Iron black color
Reddish brown to dark brown streak
5.5 hardness
Pink present in rock

Confined to zinc deposits enclosed in granular limestone

Ore of Zinc and manganese

Question 29

Chromite

Answer 29

FeCr2O4

Metallic to sub metallic luster
Iron black to brownish black (brown on fracture)
5.0 hardness
- Distinguished by submetallic luster - often appears granular with bright green alterations -

One of the first minerals to separate from cooling magma
Common constituent of peridotites (ultra mafic rocks) and other ultra mafic rocks

Only ore of chromium

Question 30

Hematite

Answer 30

Fe2O3

Reddish to reddish- brown to black color
Light to dark red streak
High specific gravity
5.5 hardness

Occurs in metamorphic deposits and as accessory minerals in feldspathic igneous rocks such as granite
May occur as sublimation from volcanic activity

Most important ore of iron for steel manufacture

Question 31

Corundum

Answer 31

Al2O3

9.0 Hardness - distinguishing property
Uneven fracture
Typically barrel shaped
Color usually some shade of brown

Found in silica deficient, aluminum rich rocks
Found in large crystals in Si-poor pegmatites

Used to make gemstones ( ruby most valuable - higher in chromium) (Sapphire - Iron and titanium present)
Also used as an abrasive

Question 32

Ilmenite

Answer 32

FeTiO3

Metallic luster
Iron black color (Distinguishing)
Black to brownish red streak
6.0 hardness
Uneven fracture

Common accessory mineral in igneous and metamorphic rocks
May be present in large masses in gabbro, diorites as a product of magmatic segregation intimately associated with magnetite
Constituent of black sand

Major source of titanium

Question 33

Rutile

Answer 33

TiO2

Adamantine to submetallic luster
Color – red to reddish-brown to black
Streak – pale brown
Very small mineral pieces

Found in granites, granite pegmatites, gneisses, mica schists, metamorphic limestone, and dolomite
May be accessory mineral in the rock or in quartz veins traversing it
Found in black sands

Used as coating of welding rods
Some titanium derived from rutile

Question 34

Cassiterite

Answer 34

SnO2

High specific gravity
6.0-7 hardness
Adamantine to submetallic luster
Brown or black
White streak

Original constituent of igneous rocks and pegmatites but more common in high temp hydrothermal veins in or near granitic rocks

Principal ore of tin

Question 35

Pyrolusite

Answer 35

MnO2

Metallic luster
Iron black
Veiny
6.0-6.5 hardness

When manganese dissolves from crystalline rocks it is redeposited primarily as pyrolusite

Primary ore of manganese

Question 36

Columbite

Answer 36

(Fe, Mn)Nb2O6 or (Fe, Mn)Ta2O6

High specific gravity
6.0 Hardness
Black to brown
Dark red to black streak
Small rocks
Recognized by - dark color with lighter streak

In granitic rocks and pegmatites - associated with quartz

Source of tantalum and niobium

Question 37

Brucite

Answer 37

Mg(OH)2

White to gray color
Pearly to vitreous luster
Perfect basal cleavage
White streak
3.5 hardness

Found in recrystallized limestone

Minor source of metallic magnesium

Question 38

Manganite

Answer 38

MnO(OH)

Metallic luster
Steel gray to iron-black color
Dark brown streak
Recognized by its black color and brown streak
5.0 hardness

Found with other manganese oxides formed by meteoric waters
Can be found in hydrothermal vein deposits, especially those associated with the deposition of manganese minerals

Minor ore of manganese

Question 39

Goethite

Answer 39

FeO(OH)

Dull luster
Yellow brown to dark brown color
Yellow brown streak
5.0 hardness
uneven fracture

Typically formed under oxidizing conditions as a weathering product of iron bearing minerals
Widespread deposits in bogs and springs

Ore of iron

Question 40

Psilomelane

Answer 40

Ba(Mn(2+))(Mn(4+))8O16(OH)4

Conchoidal fracture
Iron black - very dark
Submetallic luster
4.5 hardness

Forms as a secondary mineral through the weathering and alteration of primary manganese minerals like pyrolusite

Manganese ore

Question 41

Bauxite

Answer 41

Al2O3 . nH2O
-mixture of diaspore, gibbsite and boehmite

Dull to earthy luster
White, grey to yellow color
Pisolitic character
3.0 hardness

Supergene origin commonly produced under subtropical to tropical climatic conditions by prolonged weathering and leaching of silica from aluminum bearing rocks
From weathering of clay bearing limestone

Ore of aluminum

Question 42

Limonite

Answer 42

FeO(OH).nH2O

Dull luster
Low specific gravity
Yellow brown color and streak
Earthy fracture
5.0 hardness

Forms from the hydration of hematite and magnetite and chemical weathering of other iron rich minerals like olivine, pyroxene and biotite

Iron ore and pigment

Question 43

Halite

Answer 43

NaCl

Perfect cubic cleavage at 90 degrees
Luster - transparent to translucent
White or colorless
2.0 hardness

Dissolved in waters of springs lakes and seas - deposits formed by gradual evaporation of enclosed basins

Source of sodium and chlorine for the manufacture of HCl
Used to ice highways
Preparation of food

Question 44

Sylvite

Answer 44

KCl

White to red color - more red with impurities
More bitter than halite
2.5 hardness

formed by gradual evaporations of enclosed basins - one of the last to precipitate - after halite

Chief source of potassium which is used in fertilizer

Question 45

Fluorite

Answer 45

CaF2

Commonly green or blue
Can be scratched with knife
Vitreous luster
Octahedral cleavage - 60 and 120 degrees

Common in vugs in dolomite and limestone
Found in hydrothermal veins

Used to make HFl
Can be used in manufacturing of glass, fiberglass, pottery and enamel