Lustre metallic; H < 2

Name

Formula

Colour

Streak

G

H

System

Habit

Cleavage

F

Observations

Graphite

C

Black

Black;

Black on glazed porcelain

2.23

1

Hexagonal; hexagonal plates or massive, foliated or earthy

{0001}

perfect

7

Greasy feel; plates flexible, inelastic; marks paper; often occurs with calcite in metamorphic rocks

Stibnite

Sb2S3

Black

Grey

4.6

2

Orthorhombic; prismatic crystals elongated || c

Bladed masses

{010}

perfect

1

Brittle; occurs in quartz veins

Molybdenite

MoS2

Blue-grey

Blue-grey; greenish black on glazed porcelain

4.73

1

Hexagonal; hexagonal plates or massive, foliated

{0001}

perfect

7

Like graphite, but heavier and more metallic; marks paper; usually associated with quartz or felspar

Sylvanite

(Ag,Au)Te2

White to grey

Grey

8.1

2

Monoclinic; prismatic and tabular crystals, also massive bladed

{010}

perfect

1

Occurs in quartz veins with gold or telluride minerals

Lustre metallic; H = 2 - 5

Name

Formula

Colour

Streak

G

H

System

Habit

Cleavage

F

Observations

Goethite

HFeO2

Brown, black

Yellow to brown

4.2

5

Orthorhombic; long prismatic crystals; usually massive, botryoidal or stalactitic

{010}

perfect

7

Earthy varieties known as limonite; cement and colouring matter in sedimentary rocks; forms pseudomorphs after pyrite

Chalcopyrite

CuFeS2

Brass-yellow

Greenish black

4.3

4

Tetragonal; sphenoidal crystals; usually massive, compact

{011}

imperfect

2

Often tarnished blue or grey; occurs with pyrite, galena, sphalerite; more yellow and softer than pyrite

Manganite

MnO(OH)

Black

Brown

4.3

4

Monoclinic (pseudo-orthorhombic); prismatic crystals often elongated ||c

{010}
imperfect

7

Occurs in hydrothermal deposits; alters to pyrolusite, the streak then becoming black

Enargite

Cu3AsS4

Black

Black

4.4

3

Orthorhombic; tabular or prismatic crystals; also massive, compact or granular

{110}
perfect;
{100},
{010}
distinct

1

Often associated with chalcocite and bornite

Psilomelane

(Ba,H2O)2Mn5O10

Black

Black

4.7

5

Monoclinic; always massive, often botryoidal

None visible

7

Secondary mineral, weathering product of other Mn minerals

Covellite

CuS

Indigo-blue to black

Black

4.7

2

Hexagonal; hexagonal plates; also massive, foliated or granular

{0001}
perfect

3

Uncommon copper mineral; generally associated with chalcocite or enargite

Pyrrhotite

Fe1-xS

Bronze-yellow

Grey-black

4.6 4.65

4

Hexagonal; usually massive, granular or compact

None

3

Magnetic; surface often tarnished brown

Pentlandite

(Fe,Ni)9S8

Brass-yellow

Brown

4.6-5.0

4

Isometric; always massive

None; parting on {111}

2

Occurs intermixed with pyrrhotite

Tetrahedrite

Cu12Sb4S13

Tennantite

Cu12As4S13

Black

Brown to black

4.6-5.1

3-4

Isometric; tetrahedral crystals; also massive, granular or compact

None

2

Widely distributed in hydrothermal Cu deposits; often associated with Ag

Bornite

Cu5FeS4

Bronze-brown, purple tarnish

Grey-black

5.07

3

Isometric; usually massive, granular or compact

None

2

Often associated with chalcopyrite or chalcocite; purple tarnish often characteristic

Pyrolusite

MnO2

Grey to black

Black

5.0-5.2

To 5

Tetragonal; usually massive, columnar, fibrous or powdery

{110}
imperfect

7

Secondary after Mn minerals; often soft and earthy

 

Millerite

NiS

Pale brass-yellow

Greenish black

5.5

3-3

Trigonal; usually as hair-like crystals, often in radiating groups

{1011}, {0112}
perfect

2

Commonly occurs in cavities associated with calcite or siderite

Pyrargyrite

Ag3SbS3

Proustite

Ag3AsS3

Deep red to black

Red

5.6-5.8

2

Trigonal; prismatic crystals; also massive, granular

{1011}
good

1

Often associated with galena in lead-silver ores

Arsenic

As

Grey-white tarnishing to dark grey

Grey

5.7

3

Hexagonal; usually massive, often botryoidal

{0001}
good

-

Volatises without melting (sublimes)

Chalcocite

Cu2S

Grey to black

Grey to black

5.8

3

Orthorhombic; usually massive, compact or granular

{110}
imperfect

2

Sectile; often has a sooty coating

Bournonite

PbCuSbS3

Black

Grey-black

5.8-5.9

3

Orthorhombic; short prismatic or tabular crystals; also massive, granular or compact

{010}
imperfect

1

Occurs in veins with other sulphides, often with galena and tetrahedrite

Boulangerite

Pb5S4S11

Lead-grey

Brownish grey

6.23

2 - 3

Monoclinic; long prismatic crystals, also fibrous and hair-like

{100}
good

1

Occurs in vein deposits associated with other lead minerals

Antimony

Sb

White to grey

Grey

6.7

3

Hexagonal; usually massive, lamella

{0001}
perfect

1

Specimen often coated with white antimony oxide

Argentite

Ag2S

Black

Dark grey

7.0-7.4

2

Isometric; cubes or octahedra; also massive

{100},
{110}
imperfect

2

Sectile, occurs with other silver minerals

Wolframite

(Fe,Mn)WO4

Black

Brown-black

7.1-7.5

4

Monoclinic; crystals often tabular || {100}; also massive, bladed or compact

{010}
perfect

4

Resembles columbite-tantalite, but distinguished by perfect cleavage; occurs in quartz veins

Galena

PbS

Grey

Grey

7.6

2

Isometric; cubes or cubo-octahedra; generally massive, granular

{100}
perfect

3

The most common lead mineral; often occurs with sphalerite

Iron

Fe

Grey

Grey

7.8

4

Isometric; always massive

{100}
not prominent

6

Generally as meteorites, which always contain Ni; magnetic

Niccolite

NiAs

Copper-red

Brown-black

7.8

5

Hexagonal; usually massive, compact or granular

None

2

Often coated with green annabergite

Copper

Cu

Copper-red, often tarnished

Red; metallic

8.9

3

Isometric; massive and dendritic or wire-like forms

None

3

Often in cavities in basic igneous rocks; malleable

Calaverite

AuTe2

Brass-yellow

Green-grey

9.3

2

Monoclinic; bladed crystals or massive

None

1

Fuses easily on charcoal giving globules of Au

Bismuth

Bi

Silver-white, cream

Silver white

9.7-9.8

2

Hexagonal; indistinct crystals; often hopper shaped; usually in platy masses

{0001}
perfect

1

Occurs in quartz veins and some pegmatites; often has brassy tarnish

Silver

Ag

Silver-white, often tarnished black

Silver

10.1-11.1

3

Isometric; usually in dendritic or wire-like forms

None

3

Often occurs with barite and calcite in veins; tarnishes grey or black; malleable

Platinum

Pt

Steel-grey

Steel-grey

14 19

4

Isometric; usually in nuggets or grains

None

7

Usually as grains in alluvial deposits; may be magnetic if it contains iron

 

Gold

Au

Yellow

Yellow

15 19

3

Isometric; usually in dendritic forms or as alluvial grains

None

3

Easily recognised by its colour, softness and malleability

Lustre metallic; H > 5

Name

Formula

Colour

Streak

G

H

System

Habit

Cleavage

F

Observations

Anatase

TiO2

Usually brown

White

3.9

6

Tetragonal; usually in acute pyramidal crystals

{001}
{011}
perfect

7

Occurs in small crystals in joint planes and veins in schists and gneisses

Brookite

TiO2

Brown to black

White to grey

4.1

6

Orthorhombic; tabular and prismatic crystals

None

7

Occurs as anatase

Rutile

TiO2

Red-brown

Yellow to grey

4.2-4.3

6

Tetragonal; usually in long prismatic crystals; also massive, granular

{110}
imperfect

7

Common accessory mineral of igneous and metamorphic rocks

Chromite

(Mg,Fe)Cr2O4

Black

Brown

4.5-4.8

6

Isometric; octahedral crystals rare; usually massive, granular or compact

None

7

Occurs in ultrabasic rocks and serpentines

Ilmenite

FeTiO3

Black

Black

4.6-4.8

6

Trigonal; tabular crystals; usually massive, compact or granular

None
parting on
{0001}
{0112}

7

Occurs associated with basic igneous rocks and in sands derived from these; often with intergrown magnetite

Braunite

3Mn2O3 MnSiO3

Black

Black

4.7-4.8

6

Tetragonal; pyramidal crystals or massive granular

{112}
perfect

7

Ore mineral of manganese; occurs in veins and in metamorphic deposits

Hausmannite

Mn3O4

Black

Black

4.84

6

Tetragonal; pyramidal crystals, or massive granular

{001}
good

7

Occurs as braunite; distinguished from this mineral by brown streak

Marcasite

FeS2

Light brass-yellow

Grey-black

4.88

6

Orthorhombic; complex twinned crystals; also massive, stalactitic or nodular

{101}
imperfect

3

Occurs in low temperature surface and near surface deposits

Pyrite

FeS2

Light brass-yellow

Brown-black

5.0

6

Isometric; pyritohedra, cubes, or octahedra; also massive, compact or granular

None

3

The most common sulphide mineral; alters to limonite

Franklinite

ZnFe2O4

Black

Brown

5.1-5.3

6

Isometric; rounded octahedra or massive granular

None

7

Occurs in metamorphosed limestones at Franklin N.J; weakly magnetic

Magnetite

Fe3O4

Black

Brown to black

5.2-8.0

6

Isometric; octahedra or massive granular

None,
parting on {111}

7

Accessory mineral of igneous and metamorphic rock, and in sands; strongly magnetic

Columbite-tantalite

(Fe,Mn)(Nb,Ta)2O6

Red-brown to black

Brown to black

5.2-8.0

6

Orthorhombic; tabular or prismatic crystals, also massive

{010}
imperfect

7

Occurs in granite pegmatites

Haematite

Fe2O3

Red to black

Red-brown

5.26

6

Trigonal; tabular crystals and massive

None
parting on
{0001}
{0112}

7

Common iron mineral of sediments and metamorphosed sediments; often earthy and soft

Arsenopyrite

FeAsS

Silver-white

Grey-black

6.1

6

Monoclinic; prismatic crystals; usually massive, columnar or granular

{101}
perfect

2

Generally occurs in metalliferous veins; the most common arsenic mineral

Cobaltite

CoAsS

Silver-white

Black

6.3

6

Isometric; pyritohedra, cubes, or massive, granular or compact

{100}
perfect

3

Occurs in vein deposits; sometimes coated with pink erythrite

Skutterudite

Smaltite

Chloanthite

(Co,Ni)As3-x

Silver-white

Black

6.5

6

Isometric; cubes and octahedra, also massive, granular or compact

{100}
{111}
imperfect

3

Occurs in vein deposits; sometimes coated with pink erythrite

Uraninite

(pitchblende)

UO2

Black

Brown-black

8-10

6

Isometric; cubes; also massive, sometimes botryoidal

None

7

Occurs in granite pegmatites, hydrothermal veins, and disseminated in sandstones and limestones; yellow alteration products sometimes present

Sperrylite

PtAs2

Silver-white

Black

10.6

6

Isometric; cubic crystals and rounded grains

{001}
imperfect

2

Occurs in basic igneous rock and in sands produced from them

Lustre nonmetallic; usually colourless or white unless tinted by impurities; streak white; H < 2

Name

Formula

Colour

G

H

System

Habit

Cleavage

F

Observations

Epsomite

MgSO4 7H2O

White

1.67

2

Orthorhombic; in acicular crystals, elongated || c, or powdery crusts

{010}
good

1

Secondary mineral; soluble in H2O, salty taste

Soda-nitre

NaNO3

Colourless, white

2.25

2

Trigonal; usually in granular masses

{10111}
perfect

1

Soluble in H2O, cooling and saline taste; occurs only in rainless deserts

Gypsum

CaSO4 2H2O

Colourless, white; sometimes tinted pink, yellow, grey

2.32

2

Monoclinic; tabular prismatic crystals, elongated || c, tabular || {010}; swallow tailed twins; often granular, massive or fibrous

{010}
perfect

3

Cleavage laminae flexible but not elastic

Montmorillonite

Al2Si4O10(OH)2 xH2O

White, grey, green-grey

2.0-2.7

2

Monoclinic; always in clayey masses

{001}
perfect, not megascopically observable

7

Clay mineral; absorbs water with swelling; often has soapy feel

Brucite

Mg(OH)2

Colourless, white; pale green

2.4

2

Trigonal; in hexagonal plates or massive compact; sometimes fibrous

{0001}
perfect

7

Occurs in association with dolomite or serpentine or in metamorphosed dolomite

Kaolinite

Al4Si4O10(OH)8

White, grey, brown

2.6

2

Triclinic; always in clayey masses

{001}
perfect
not usually observable

7

Clay mineral; clayey odour when breathed upon; does not swell in water

Talc

Mg3Si4O10(OH)2

Green

2.82

1

Monoclinic; in foliated or fine-grained masses

{001}
perfect

7

Greasy feel; occurs in magnesium rich metamorphic rocks

Pyrophyllite

Al2Si4O10(OH)2

White, yellow, brown

2.84

1

Monoclinic; radiated fibrous or fine grained

{001}
perfect

7

Greasy feel; occurs in aluminium rich metamorphic rocks

 

 

Lustre nonmetallic; usually colourless or white unless tinted by impurities; streak white; H = 2 - 5

Name

Formula

Colour

G

H

System

Habit

Cleavage

F

Observations

Carnallite

KMgCl3 6H2O

Colourless or white

1.60

2

Orthorhombic; usually in coarsely granular masses

None

1

Bitter taste, occurs in salt deposits; deliquescent

Borax

Na2B4O5(OH)4 8H2O

White

1.71

2

Monoclinic; short prismatic crystals

{100}
indistinct

1

Sweetish alkaline taste; deposited from salt lakes; effloresces in dry air

Kernite

Na2B4O7 4H2O

Colourless

1.91

2

Monoclinic; massive, large cleavages

{100}
perfect
{001}
good

1

Fibrous fracture; sometimes coated with white tincalconite, Na2B4O7 5H2O

Sylvite

KCl

Colourless, sometimes white or grey

1.99

2

Isometric; cubic crystals; usually massive, granular

{100}
perfect

2

Salty taste like halite, but somewhat bitter, sectile

Opal

SiO2 nH2O

Colourless, white

2.0 - 2.2

5 -5

Amorphous; massive compact, sometimes mamillary

None

7

Secondary silica deposited at low temperatures

Chabazite

CaAl2Si4O12 6H2O

Colourless, white, pink

2.1

4

Trigonal; usually in cube-like rhombohedral crystals

{1011}
perfect

3

Occurs in cavities in basalts; crystal form distinguishes it from other zeolites

Stilbite

CaAlSi7O18 7H2O

White, pale yellow

2.1-2.2

4

Monoclinic; sheaf-like aggregates of twinned crystals

{010}
perfect

3

Occurs in cavities in basalts; crystal form distinguishes it from other zeolites

Halite

NaCl

Colourless, white, red

2.16

2

Isometric; cubic crystals; usually massive, granular

{100}
perfect

2

Characteristic salty taste

Heulandite

CaAl2Si7O18 6H2O

White

2.2

3 4

Monoclinic; trapezoidal crystals tabular || {010}

{010}
perfect

3

Pearly lustre on cleavage; occurs in basalts; crystal form distinguishes it from other zeolites

Natrolite

Na2Al2Si3O10 2H2O

Colourless, white

2.55

5

Orthorhombic; long prismatic crystals and radiating nodular form

{110}
perfect

3

Occurs in cavities in basalts; crystal form distinguishes it from other zeolites

Laumonite

CaAl2Si4O12 4H2O

White

2.25-2.30

4

Monoclinic; small prismatic crystals; also massive, often powdery

{010}
{110}
perfect

3

Occurs in cavities in basalts; crystal form distinguishes it from other zeolites

Analcime

NaAlSI2O6 6H2O

Colourless, white

2.3

5

Isometric; trapezoidal crystals; also massive, compact or granular

None

4

Occurs in cavities in basalts with other zeolites, also in some igneous and sedimentary rocks

Apophyllite

KCa4(Si4O10)F 8H2O

Colourless, white

2.35

5

Tetragonal; prismatic crystals with basal plane and pyramids

{001}
perfect

2

Occurs in cavities in basalts and in hydrothermal veins, often with zeolites

Gibbsite

Al(OH)3

White, red, brown

2.3-2.4

3

Monoclinic; usually massive, compact, pisolitic, or earthy

{001}
perfect

7

A major component of bauxite

Colemanite

CaB3O4(OH)3 H2O

Colourless, white

2.42

4

Monoclinic; short prismatic crystals, often with complex terminations; also massive

{010}
perfect
{001}
imperfect

2

Occurs as geode-like masses in sedimentary rocks

Calcite

CaCO3

Colourless, white

2.71

3

Trigonal; scalenohedral and rhombohedral crystals; also massive, granular or compact

{1011}
perfect

7

Often coloured brown, grey, or black with impurities; effervesces in cold dilute HCl

Dolomite

CaMg(CO3)2

White, yellow, pink

2.85

3 - 4

Trigonal; small curved rhombohedral crystals; also massive, granular

{1011}
perfect

7

Effervesces in warm dilute HCl

Alunite

KAl3(SO4)2(OH)6

White, pink

2.6 2.9

3-4

Trigonal; usually massive, granular or compact

{0001}
perfect

7`

Often occurs in hydrothermal alteration of volcanic rocks

Muscovite

KAl2(AlSi3O10)(OH)2

Colourless or pale tints

2.8-2.9

2-3

Monoclinic; usually in irregular platy crystals; also massive, sometimes compact

{001}
perfect

2

Large crystals in granite pegmatites, small flakes in many metamorphic rocks

Pectolite

Ca2NaHSi3O9

White

2.86

5

Triclinic; usually in radiating aggregates of needle-like crystals

{001}
{100}
perfect

3

Typically occurs associated with zeolites in cavities in basalts

Wollastonite

CaSiO3

White

2.9

5

Triclinic; usually in columnar or fibrous masses

{100}
perfect
{102}
{001}
good

4

Occurs in metamorphosed limestones

Aragonite

CaCO3

White

2.93

3-4

Orthorhombic; hexagonal twinned crystals; also massive, sometimes coralloid

{010}
imperfect

7

Effervesces in cold dilute HCl; much less common than calcite

Cryolite

Na3AlF6

White

2.96

2

Monoclinic; usually massive, coarsely granular

None
parting on
{001}
{110}

2

Wet-snow lustre; occurs in large amounts at Ivigtut, Greenland, associated with siderite

Anhydrite

CaSO4

White, grey, pale blue

3.0

3

Orthorhombic; usually massive, granular

{010}
perfect
{100}{001}
good

3

Forms extensive belts in sedimentary rocks, alters to gypsum

Magnesite

MgCO3

White

3.0

4

Trigonal; usually massive, compact

{1011}
perfect

7

Cleavage not seen in compact forms, which have conchoidal fracture; effervesces in warm dilute HCl

Boehmite

ALO(OH)

White, yellow, brown

3.0-3.1

3

Orthorhombic; always massive, compact; often pisolitic

{010}
not visible

7

Important constituent of bauxite

Amblygonite

LiAlPO4(OH)2 H2O

White

3.1

5

Triclinic; usually in cleavable masses

{100}
perfect;
{110}{011}
distinct

2

Often shows twinning striations on cleavages; occurs in granite pegmatites

Hemimorphite

Zn4Si2O7(OH)2 H2O

White

3.4-3.5

5

Orthorhombic; usually massive, often in mammillary forms

{110}
perfect

6

Alteration product of sphalerite; often associated with smithsonite

Periclase

MgO

White

3.56

5

Isometric; usually in small rounded grains

{100}
perfect

7

Occurs as small grains often altered to brucite in metamorphosed dolomite

Strontianite

SrCO3

White

3.78

3

Orthorhombic; usually massive, columnar to fibrous

{110}
good

6

Red flame colouration; effervesces in cold dilute HCl

Celestite

SrSO4

White, pale blue

3.9 4.0

3

Orthorhombic; crystals tabular || {001}, also massive, often fibrous

{001}
perfect
{201}
good

3

Red flame colouration

Witherite

BaCO3

White

4.31

3

Orthorhombic; hexagonal twinned crystals, also massive, columnar or granular

{010}
distinct

3

Green flame colouration; effervesces in cold dilute HCl

Smithsonite

ZnCO3

White, yellow, blue, green

4.4

4

Trigonal; usually massive compact, often concretionary

{1011}
good

7

Effervesces in warm dilute HCl

Barite

BaSO4

Colourless, white, grey

4.5

3

Orthorhombic; crystals usually tabular ||{001}, also massive, granular

{001}
{210}
perfect

3

Green flame colouration

Scheelite

CaWO4

White, yellow, brown

6.1

5

Tetragonal; usually massive, granular

{101}
distinct

5

Fluoresces white or yellow in ultra violet light

 

Anglesite

PbSO4

White, grey

6.3-6.4

3

Orthorhombic; crystals prismatic or tabular ||{001}; also massive , compact

{001}
{210}
distinct

2

Often has a nucleus of unchanged galena

Cerussite

PbCO3

White, grey

6.6-6.6

3

Orthorhombic; in lattice-like aggregates of twinned crystals; also massive, granular

{110}
{021}
distinct

2

Effervesces weakly in cold dilute HCl, strongly in warm

Mimetite

Pb5(AsO4)3Cl

White, yellow

7.2 7.3

4

Hexagonal; in small prismatic crystals; also massive, often globular and botryoidal

None

1

Found in the oxidised zone of lead deposits

Lustre nonmetallic; usually colourless or white unless tinted by impurities; streak white; H > 5

Name

Formula

Colour

G

H

System

Habit

Cleavage

F

Observations

Tridymite

SiO2

Colourless, white

2.26

6

Hexagonal; small thin hexagonal plates, often twinned

{1010}
imperfect

7

Occurs in cavities in volcanic rocks

Cristobalite

SiO2

White

2.32

6

Isometric; minute octahedra or small rounded aggregates

None

7

Occurs as isolated crystals in basic volcanic rocks

Leucite

KalSi2O6

White, grey

2.45

6

Isometric; trapezohedral crystals

{110}
imperfect

7

Occurs as isolated crystals in volcanic rocks

Nepheline

NaAlSiO4

White, brown, grey

2.5 2.6

6

Hexagonal; hexagonal prisms, and massive granular

{1010}
imperfect

4

Gelatinises in HCl

Orthoclase

KalSi3O8

White, pink

2.56

6

Monoclinic; prismatic crystals, flattened || {010} or elongated || a; also massive, granular

{001}
perfect
{010}
good

5

Occurs in potassium rich igneous and metamorphic rocks

Microcline

KalSi3O8

White, pink, green

2.56

6

Triclinic; like orthoclase

{001}
perfect
{010}
good

5

Like orthoclase, but may show imperfect polysynthetic twinning striations, or grid structure on {001}; green colour sometimes characteristic

Scapolite

(Na,Ca)4[(Al,Si)4O8]3
(Cl,CO3

White, yellow, pink, grey

2.56 2.77

6

Tetragonal; prismatic crystals terminated by pyramids; also massive, granular or columnar

{100}
{110}
good

3

Occurs in lime-rich metamorphic rocks

Plagioclase

(Na,Ca)(Al,Si)4O8

White, grey, brown

2.62 2.76

6

Triclinic; prismatic crystals, flattened || {010}: also massive, granular

{001}
perfect
{010}
good

4-5

Polysynthetic twinning usually visible on {001} cleavage surface

Quartz

SiO2

Colourless, white, grey, pink, green

2.65

7

Trigonal; prismatic crystals terminated by rhombohedra; also massive, granular or compact (chalcedony)

None

7

Occurs in silica rich igneous rocks, granite pegmatites, sedimentary and metamorphic rocks

Anthophyllite

(Mg,Fe)7Si8O22

White, grey, pink

2.9 3.3

6

Orthorhombic; massive, bladed or fibrous aggregates

{210}
perfect

6

Occurs in magnesium rich metamorphic rocks

Tremolite

Ca2Mg5Si8O22(OH)2

White

3.0

6

Monoclinic; usually in columnar or fibrous aggregates

{11}
perfect

4

Occurs in calcareous and magnesian metamorphic rocks, associated with calcite, dolomite, talc

Datolite

Ca(OH)BSiO4

Colourless, pale yellow, pale green, white

3.0

6

Monoclinic; short prismatic crystals; also massive, granular or compact

None

2

Occurs in cavities in basic igneous rocks associated with zeolites

Lawsonite

CaAl2Si2O7(OH)2 H2O

White, pink, grey

3.1

8

Orthorhombic; prismatic crystals and tabular crystals; also massive, granular or compact

{010}
{001}
perfect

4

Occurs in schists and gneisses with glaucophane

Spodumene

LiAlSi2O6

Colourless, white, pink

3.1 3.2

6

Monoclinic; long prismatic crystals, also platy masses

{110}
perfect
parting on {100}

4

Red flame colouration; occurs in granite pegmatites

Andalusite

Al2SiO5

White, grey, pink, brown

3.15

7

Orthorhombic; coarse prismatic crystals, square cross section; also massive, columnar or granular

{110}
good

7

Often contains inclusions symmetrically arranged (var. chiastolite); typically occurs in hornfels

Sillimanite

Al2SiO5

White, brown, grey

3.24

7

Orthorhombic; usually in fibrous aggregates

{010}
perfect

7

Occurs in high grade schists and gneisses

Diaspore

AlO(OH)

White, grey, brown

3.3 - 3.4

6

Orthorhombic; usually massive, bladed, foliated, or compact

{010}
perfect

7

Occurs in aluminium rich metamorphic rocks

Diamond

C

Colourless, yellow, pink ,grey, black

3.5

10

Isometric; rounded octahedral crystals, often twinned

{111}
perfect

7

Occurs in ultrabasic igneous rocks or sands derived from them

Topaz

Al2SiO4(OH,F)2

Colourless, white, yellow, blue

3.5 3.6

8

Orthorhombic; prismatic crystals terminated by pyramids; also massive, granular

{001}
perfect

7

Occurs in veins and cavities in silica rich igneous rocks and pegmatites

Lustre nonmetallic; usually coloured; streak white unless otherwise stated; H < 2

Name

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

Melanterite

FeSO4 7H2O

Pale green

1.90

2

Monoclinic; usually stalactitic or powdery crusts

{001}
perfect

1

Secondary mineral after iron sulphides; soluble in H2O; tastes like ink

Vermiculite

Mg3Si4O10(OH)2 xH2O

Yellow, brown, green

2.4

1

Monoclinic; pseudo-hexagonal plates, pseudomorphs after biotite

{001}
perfect

7

Expands enormously when heated; occurs in magnesium rich rocks

Glauconite

K(Fe,Mg,Al)2Si4O10

Dark green to black

2.5 2.8

2

Monoclinic; occurs as rounded grains

{001}
perfect;
not megascopically observable

3

Streak pale green; occurs in marine sedimentary rocks as pure beds or as grains in limestone, sandstone, mudstone

Chlorite

(Mg,Fe,Al)6(Al,Si)4O10
(OH)8

Green

2.6 3.4

2

Monoclinic; in pseudo-hexagonal plates or micaceous masses

{001}
perfect

5

Cleavage laminae flexible but not elastic; common in schists

Vivianite

Fe3(PO4)2 8H2O

Blue, blue-green

2.7

1

Monoclinic; in prismatic crystals, elongated || c, or earthy masses

{010}
prominent in crystals

2

Streak blue; earthy masses in clay and fossil bones; crystals associated with iron sulphides in ore deposits

Erythrite

Co3(AsO4)2 8H2O

Carmine-red

3.06

1

Monoclinic; prismatic crystals and powdery masses

{010}
perfect

3

Streak pink, occurs as coatings or crusts on cobalt arsenides

Autunite

Ca(UO2)(PO4)2

10-12H2O

Lemon-yellow

3.1 3.2

2 2

Tetragonal; thin tabular on {001}; scaly aggregates

{001}
perfect

3

Streak yellow; occurs as an oxidation product from veins or pegmatites containing uraninite

Torbernite, Metorbernite

Cu(UO2)(PO4)2

8-12H2O

Emerald-green to apple-green

3.2 3.7

2 2

Tetragonal; tabular on {001}; foliated or micaceous

{001}
perfect

3

Streak green; occurs as an oxidation product over veins containing uraninite and copper sulphides

Orpiment

As2S3

Yellow

3.48

1

Orthorhombic; acicular crystals, elongated || c; usually in foliated or granular masses

{001}
perfect

1

Streak yellow; often occurs with realgar

Realgar

AsS

Red

3.56

2

Monoclinic; short prismatic crystals; usually in granular masses

{010}
distinct

1

Streak orange; often occurs with orpiment

Tyuyamunite

Ca(UO2)2(VO4)2 6H2O

Yellow, greenish yellow

3.6 4.4

2

Orthorhombic; usually massive, powdery

{001}
perfect, seldom visible

3

Streak yellow; occurs disseminated in sandstone and as crusts on limestone

Carnotite

K2(UO2)2(VO4)2 3H2O

Yellow

4 5

2

Monoclinic; usually massive, powdery

{001}
perfect, seldom visible

7

Streak yellow; occurs disseminated in sandstone; like tyuyamunite only rarer

Cerargyrite

AgCl

Colourless, yellow, grey

5.6

2

Isometric; usually massive, wax-like

None

1

Sectile; occurs in oxidised zone of silver deposits

Lustre nonmetallic; usually coloured; streak white unless otherwise stated; H= 2 - 5

Name

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

Sulphur

S

Yellow

2.07

2

Orthorhombic; pyramidal crystals; usually massive, granular or compact

{001}
{110}
{111}
imperfect

1

Burns, giving choking fumes of SO2; deposited in fumaroles, and occurs in limestones and gypsum

Chalcanthite

CuSO4 5H2O

Blue

2.28

2

Triclinic; short prismatic crystals; also massive, granular

{110}

3

Streak pale blue; metallic nauseous taste; occurs in oxidised zone of sulphide copper ores

Chrysocolla

CuSiO3 2H2O

Blue, green

2.4

2 - 4

Orthorhombic (?); always massive, compact

None

7

Secondary mineral in oxidised copper ores

Serpentine

Mg6Si4O10(OH)8

Green, yellow, brown, grey

2.5 2.6

2

Monoclinic; always massive, compact or fibrous (asbestos)

None visible

7

Alteration product of ultrabasic igneous rocks

Garnierite

(Mg,Ni)6Si4O10(OH)8

Apple-green

2.5 2.6

2

Monoclinic; always massive, often as porous crusts

None visible

7

A nickel bearing serpentine

Lepidolite

KLi2Al(Si4O10)(OH)2

Colourless, mauve, grey

2.8 2.9

2 - 3

Monoclinic; usually massive, course to fine granular

{001}
perfect

2

Pale mauve colour often diagnostic; occurs in granite pegmatites

Phlogopite

KMg3(AlSi3O10)(OH)2

Pale brown

2.8 2.9

2 - 3

Monoclinic; usually in irregular platy crystals

{001}
perfect

4

Occurs in ultrabasic rocks and metamorphosed dolomites

Biotite

K(Mg,Fe)3AlSi3O10

(OH)2

Green, brown, black

2.9 3.4

2

Monoclinic; usually in irregular platy crystals

{001}
perfect

3

Occurs in acid igneous rocks, pegmatites, and metamorphic rocks

Jarosite

Kfe3(SO4)2(OH)6

Brown

2.9 3.3

3

Trigonal; usually massive, compact

{0001}
perfect

5

Resembles limonite, but contains sulphate; yellow streak

Fluorite

CaF2

Purple, green, yellow, colourless

3.18

4

Isometric; cubic crystals, often twinned on {111}; also massive, granular

{111}
perfect

3

Common vein mineral, and replacing limestones and dolomites

Apatite

Ca5(PO4)3F

Green, blue, brown, white

3.1 3.2

5

Hexagonal; prismatic crystals, also massive, granular or compact

{0001}
poor

5

Occurs in pegmatites and metamorphosed limestones; also in sedimentary rocks (phosphorite)

Kyanite

Al2SiO5

Blue, green, white

3.63

4 7

Triclinic; usually in bladed crystals

{100}
perfect
{010}
good

7

Occurs in aluminium rich schists and gneisses

Rhodochrosite

MnCO3

Pink

3.7

3 - 4

Trigonal; usually massive, granular

{1011}
perfect

7

Effervesces in warm dilute HCl; occurs in ore deposits

Atacamite

Cu2(OH)3Cl

Green

3.76

3

Orthorhombic; slender prismatic crystals; also massive granular

{010}
perfect

3

Streak green; associated with other secondary copper minerals; gives azure blue flame colouration

Azurite

Cu3CO3)2(OH)2

Blue

3.77

4

Monoclinic; crystals of various habits, also massive, spherical aggregates

{011}
good

3

Streak blue; effervesces in cold dilute HCl

Siderite

FeCO3

Yellow, brown

3.8 4.0

4

Trigonal; rhombohedral aggregates, also massive, granular to compact

{1011}
perfect

5

Effervesces in warm dilute HCl; occurs in veins and replacement of limestone

Antlerite

Cu3(SO4)(OH)4

Dark green

3.88

3

Orthorhombic; usually in granular masses or cross fibre veinlets

{010}
perfect

4

Streak green; soluble in HCl without effervescence

Wurtzite

ZnS

Brownish-black

4.09

3 - 4

Hexagonal; pyramidal or prismatic crystals; usually massive, fibrous, columnar, or as banded crusts

{1120}
distinct

6

Streak brown; much less common than sphalerite

Sphalerite

(Zn,Fe)S

Yellow, brown, black

4.0 4.1

4

Isometric; usually massive, coarse to fine granular

{110}
perfect

6

Dissolves in warm HCl giving off H2S

Brochanite

Cu4(SO4)(OH)6

Green

4.0

4

Monoclinic; prismatic to acicular crystals; also massive granular

{100}
perfect

4

Streak green; dissolves in cold dilute HCl without effervescence

Malachite

Cu2(CO3)(OH)2

Green

4.0

4

Monoclinic; usually massive compact, often stalactitic or botryoidal

{201}
perfect

3

Streak green; effervesces in cold dilute HCl

Goethite

(Limonite)

HFeO2

Yellow, brown

4.2

3 -5

Orthorhombic; usually massive, compact or earthy, also stalactitic

{010}
perfect

6

Streak yellow; dissolves in dilute HCl giving a yellow solution

Pyrochlore-microlite

NaCa(Nb,Ta)2O6F

Yellow, brown, black

4.2 6.4

5

Isometric; octahedral crystals and rounded grains

Generally absent

7

Occurs in carbonatites (pyrochlore) and granite pegmatites

Xenotime

YPO4

Yellowish to reddish brown

4.4 5.1

4 5

Tetragonal prismatic with pyramidal faces resembling zircon

{100}
perfect

7

Accessory mineral in acidic igneous rocks, pegmatites and gneisses

Monazite

CePO4

Yellow, brown

4.6 5.4

5

Monoclinic; small crystals flattened || {100}, also as detrital grains

Parting on {001}

7

Accessory mineral in granites and pegmatites; concentrates in sands and sandstones

Thorite

ThSiO4

Orange, brown, black

5.2 6.7

5

Tetragonal; pyramidal crystals; also massive, compact

{100}
perfect

5

Strongly radioactive; occurs in pegmatites; concentrates in sands and as detrital grains

Zincite

ZnO

Red

5.7

4

Hexagonal; usually in platy masses or rounded grains

{0001}
perfect

7

Streak orange; occurs with franklanite and willemite at Franklin N.J.

Crocoite

PbCrO4

Orange-red

6.1

3

Monoclinic; usually in prismatic crystals

{110}
imperfect

2

Streak orange-yellow; rare secondary mineral in lead veins

Cuprite

Cu2O

Red, often tarnished

6.1

4

Isometric; cubic crystals, also massive, granular or hair-like

{111}
imperfect

3

Streak red-brown; easily reduced to copper on charcoal

Vanadinite

Pb5(PO4)3Cl

Yellow, red, brown

6.9

3

Hexagonal; usually in small hexagonal prisms

None

2

Streak yellow; found in oxidation zone of lead deposits

Wulfenite

PbMoO4

Yellow, red, brown

6.5 7.0

3

Tetragonal; usually in square platy crystals, tabular || {001}

{010}
distinct

2

Often associated with vanadinite

Pyromorphite

Pb5(PO4)3Cl

Green, yellow, brown

7.0 7.1

4

Hexagonal; in small prismatic crystals; also massive, often globular and botryoidal

None

1

Found in the oxidised zone of lead deposits

Cinnabar

HgS

Red

8.1

2

Hexagonal; usually massive, granular

{1010}
perfect

1

Streak red, volatises on heating

 

Lustre nonmetallic; usually coloured; streak white unless otherwise stated; H > 5

Name

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

Sodalite

Na8(AlSiO4)6Cl2

Blue, white, pink

2.3

6

Isometric; usually massive, granular

{110}
perfect

4

Blue colour characteristic; occurs in nepheline syenites

Cancrinite

Na8(AlSiO4)6

Yellow, white, pink

2.4 2.5

6

Hexagonal; usually massive, granular

{1010}
perfect

2

Effervesces in warm dilute HCl; its yellow colour often characteristic

Cordierite

(Mg,Fe)2Al4Si5O18

Colourless, blue, grey, brown

2.55 2.75

7

Orthorhombic; usually massive, granular

{010}
perfect

5

Occurs in aluminous metamorphic rocks

Turquoise

CuAl6(PO4)4(OH)8.4H2O

Blue, green

2.6 2.8

6

Triclinic; usually massive, compact

{001}
perfect

7

Occurs in veinlets in igneous and sedimentary rocks

Beryl

Be3Al2Si6O18

Colourless, white, green, yellow, blue

2.65 2.85

8

Hexagonal; prismatic crystals or massive, granular

{0001}
imperfect

5

Occurs in granite pegmatites

Allanite

(Ca,Ce)2(Al,Fe)3

Si3O12OH

Black, dark brown

2.7 4.0

6

Monoclinic; platy or columnar crystals, also massive, granular

{001}
seldom observable

3

Streak grey or green grey; often somewhat radioactive

Prehnite

CaAl2Si3O10(OH)2

White, pale green

2.9

6

Orthorhombic; generally massive, encrusting with crystalline surface

{001}
not prominent

2

Occurs in cavities in basic igneous rocks associated with zeolites

Tourmaline

Na,Mg,Fe,Al borosilicate

Black, brown, pink, green, blue

3.0 3.4

7

Trigonal; prismatic crystals with rounded trigonal cross section; also massive, columnar

None

6

Prism faces striated; occurs in granite pegmatites, and schists and gneisses

Actinolite

Ca2(Mg,Fe)5Si8O22

Green

3.0 3.4

6

Monoclinic; usually in columnar or fibrous aggregates

{110}
perfect

3

Occurs in schists and gneisses

Hornblende

NaCa2(Mg,Fe,Al)5

(Al,Si)8O22(OH)2

Green, brown, black

3.0 3.4

6

Monoclinic; long prismatic crystals, also columnar, fibrous or granular

{110}
perfect

3

A common mineral of both igneous and metamorphic rocks

Glaucophane

Na2Mg3Al2Si8O22(OH)2

Blue, lavender, blue-black

3.1 3.3

6

Monoclinic; in aggregates of bladed or acicular crystals, or as felt or silky needles

{110}
perfect

3

Occurs in schists and gneisses

Dumortierite

(Al,Fe)2BSi3O18

Blue, pink

3.3 3.4

7

Orthorhombic; usually massive, or fibrous compact

{100}
distinct

7

Occurs in aluminium rich metamorphic rocks

Cummingtonite

(Fe,Mg)2Si8O22(OH)2

Brown

3.2 3.6

6

Monoclinic; usually massive, fibrous aggregates

{110}
perfect

4

Occurs in iron rich schists and gneisses

Enstatite

(Mg,Fe)SiO3

White, pale green, brown, grey

3.2 3.4

6

Orthorhombic; usually massive, fibrous or granular

{210}
good

6

Often has a bronze colour (var. bronzite)

Augite

(Ca,Mg,Al,Fe)(Al,Si)2O6

Black, dark green

3.25 3.55

6

Monoclinic; short prismatic crystals; also massive, granular

{110}
good

4

The common pyroxene of igneous rocks

Diopside

Ca(Mg,Fe)Si2O6

White, green

3.25 3.40

6

Monoclinic; prismatic crystals, usually massive, granular

{110}
good

4

Occurs in metamorphosed dolomites

Axinite

Ca,Mn,Fe,Al borosilicate

Brown, yellow

3.3

7

Triclinic; wedge shaped crystals, also massive granular

{100}
good

2

Occurs in contact zones of igneous intrusions

Jadeite

NaAlSi2O6

White, green

3.3

6

Monoclinic; usually massive, granular to compact

{110}
good

3

Metamorphic mineral often associated with serpentine

Zoisite

Ca2AL3Si2O12(OH)

Grey, green, pink

3.3

7

Orthorhombic; usually massive; columnar or bladed

{001}
perfect

3

Occurs in metamorphic rocks rich in lime and alumina

Riebeckite

Na2(Mg,Fe)5Si8O22

Dark blue, black

3.3 3.6

6

Monoclinic; bladed crystals, also massive granular; sometimes asbestiform

{110}
perfect

2

Blue-grey streak; occurs in soda rich igneous rocks

Olivine

(Mg,Fe)2SiO4

Olive-green

3.3 3.6

6

Orthorhombic; usually massive, granular

{010}
imperfect

7

Occurs in basic and ultrabasic igneous rocks

Idocrase

Ca,Mg,Al silicate

Brown, green, yellow, blue

3.3 3.5

7

Tetragonal; short prismatic or low pyramidal crystals; also massive granular

{100}
imperfect

3

Occurs in metamorphosed limestones

Clinozoisite, Epidote

Ca2(Al,Fe)3Si3O12(OH)

Green to black

3.3 3.6

7

Monoclinic; prismatic crystals elongated || b; Also massive, columnar or granular

{100}
perfect

3

Yellow-green colour typical; occurs in metamorphic rocks

Hedenbergite

Ca(Fe,Mg)Si2O6

Green to black

3.40 3.55

6

Monoclinic; usually massive, granular or fibrous

{110}

4

Often occurs in skarn associated with ore deposits

Hypersthene

(Mg,Fe)SiO3

Brown, black

3.4 4.0

6

Orthorhombic; usually massive, platy

{210}
good

4

Occurs in basic igneous rocks

Sphene

CaTiSiO5

Brown, yellow, green

3.5

6

Monoclinic; usually in small diamond or wedge shaped crystals

{110}
imperfect

3

An accessory mineral of igneous and metamorphic rocks

Rhodonite

MnSiO3

Pink

3.5 3.7

6

Triclinic; tabular crystals; usually massive, granular to compact

{110}
{110}
good

3

Often veined with black manganese oxides

Aegirine

NaFeSi2O6

Dark green brown, black

3.6

6

Monoclinic; usually in prismatic crystals, often elongated || c

{110}
perfect

2

Occurs in sodium rich igneous rocks

Spinel

MgAl2O4

Black, brown, green, red, blue

3.6

8

Isometric; octahedral crystals, often twinned on {111}

{111}
imperfect

7

Occurs in metamorphic rocks and ultrabasic igneous rocks, and in sands derived from them

Grossularite

Ca3Al2Si3O12

White, yellow, pink, brown

3.6 3.7

7

Isometric; dodecahedra and trapezohedra and combinations; also massive, granular or compact

None

3

Occurs in metamorphosed limestones

Pyrope

Mg3Al2Si3O12

Red

3.6 3.9

7

Isometric; usually in anhedral grains

None

4

Occurs in high grade metamorphic rocks

Andradite

Ca3Fe2Si3O12

Yellow, green, brown, black

3.7 3.8

7

Isometric; dodecahedra and trapezohedra and combinations; also massive, granular

None

3

Occurs in metamorphosed limestones often associated with ore deposits

Chrysoberyl

BeAl2O4

Yellow, green, brown

3.7

8

Orthorhombic; crystals tabular || {001}, and pseudohexagonal twins

{110}
distinct

7

Occurs in granite pegmatites and in alluvial deposits

Staurolite

FeAl4Si2O10(OH)2

Brown

3.76

7

Orthorhombic; prismatic crystals, often twinned in right angle and diagonal crosses

{010}
distinct

6

Occurs in medium grade schists and gneisses

Uvarovite

Ca3Cr2Si3O12

Green

3.8

7

Isometric; usually in dodecahedra

None

6

Generally associated with serpentine and chromite

Willemite

Zn2SiO4

Yellow, green, brown, black

3.9 4.2

6

Trigonal; usually massive, granular

{0001}
{1120}
imperfect

4

Often fluoresces green in ultraviolet light

Zircon

ZrSiO4

Brown, grey

3.9 4.7

7

Tetragonal; prismatic crystals terminated by pyramids and as rounded grains

{100}
imperfect

7

An accessory mineral of igneous and metamorphic rocks; a detrital mineral in sands

Anatase

TiO2

Usually brown

3.9

6

Tetragonal; usually in acute pyramidal crystals

{001}
{011}
perfect

7

Occurs in small crystals in joint planes and veins in aluminium rich igneous rocks

Corundum

Al2O3

Grey, blue, pink, brown

4.0

9

Trigonal; hexagonal prisms and pyramids, also massive, granular

None;
parting on {0001}
{0112}

7

Occurs in metamorphic rocks and occasionally in aluminium rich igneous rocks

Almandite

Fe3Al2Si3O12

Red to black

4.0 4.3

7

Isometric; dodecahedra, trapezohedra and combinations, also massive, granular

None

3

Occurs in metamorphic rocks; the most common garnet

Spessartite

Mn3Al2Si3O12

Orange, red, brown

4.0 4.2

7

Isometric; trapezohedra often combination with dodecahedra, also massive, granular

None

3

Occurs in granite pegmatites and metamorphosed manganese rich rocks

Brookite

TiO2

Brown to black

4.1

6

Orthorhombic; tabular and prismatic crystals

None

7

Occurs in joint planes and veins in schists and gneisses

Rutile

TiO2

Red-brown to black

4.2 4.5

6

Tetragonal; usually in long prismatic crystals or massive

{110}
perfect

7

Common accessory mineral of igneous and metamorphic rocks

Cassiterite

SnO2

Brown to black

7.0

6

Tetragonal; prismatic crystals and massive, sometimes botryoidal or concretionary

{110}
imperfect

7

Occurs in quartz veins and granite pegmatites; also detrital