Formula

Colour

Streak

G

H

Habit

Cleavage

F

Observations

C

Black

Black on glazed porcelain

2.23

1

Hexagonal; hexagonal plates or massive, foliated or earthy

perfect

7

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

Sb₂S₃

Black

Grey

4.6

2

Bladed masses

perfect

1

Brittle; occurs in quartz veins

MoS₂

Blue-grey

Blue-grey; greenish black on glazed porcelain

4.73

1

Hexagonal; hexagonal plates or massive, foliated

perfect

7

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

(Ag,Au)Te₂

White to grey

Grey

8.1

2

Monoclinic; prismatic and tabular crystals, also massive bladed

perfect

1

Occurs in quartz veins with gold or telluride minerals

Formula

Colour

Streak

G

H

Habit

Cleavage

F

Observations

HFeO₂

Brown, black

Yellow to brown

4.2

5½

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

perfect

7

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

CuFeS₂

Brass-yellow

Greenish black

4.3

4

Tetragonal; sphenoidal crystals; usually massive, compact

imperfect

2

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

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

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

(Ba,H₂O)₂Mn₅O₁₀

Black

Black

4.7

5½

Monoclinic; always massive, often botryoidal

None visible

7

Secondary mineral, weathering product of other Mn minerals

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

Fe_1-xS

Bronze-yellow

Grey-black

4.6 – 4.65

4

Hexagonal; usually massive, granular or compact

None

3

Magnetic; surface often tarnished brown

(Fe,Ni)₉S₈

Brass-yellow

Brown

4.6-5.0

4

Isometric; always massive

None; parting on {111}

2

Occurs intermixed with pyrrhotite

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

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

MnO₂

Grey to black

Black

5.0-5.2

To 5½

Tetragonal; usually massive, columnar, fibrous or powdery

{110}
imperfect

7

Secondary after Mn minerals; often soft and earthy

NiS

Pale brass-yellow

Greenish black

5.5

3-3½

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

{101’1}, {011’2}
perfect

2

Commonly occurs in cavities associated with calcite or siderite

Ag₃AsS₃

Deep red to black

Red

5.6-5.8

2½

Trigonal; prismatic crystals; also massive, granular

{101’1}
good

1

Often associated with galena in lead-silver ores

As

Grey-white tarnishing to dark grey

Grey

5.7

3½

Hexagonal; usually massive, often botryoidal

{0001}
good

-

Volatises without melting (sublimes)

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

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

Pb₅S₄S₁₁

Lead-grey

Brownish grey

6.23

2½ - 3

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

{100}
good

1

Occurs in vein deposits associated with other lead minerals

Sb

White to grey

Grey

6.7

3

Hexagonal; usually massive, lamella

{0001}
perfect

1

Specimen often coated with white antimony oxide

Ag₂S

Black

Dark grey

7.0-7.4

2½

Isometric; cubes or octahedra; also massive

{100},
{110}
imperfect

2

Sectile, occurs with other silver minerals

(Fe,Mn)WO₄

Black

Brown-black

7.1-7.5

4½

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

PbS

Grey

Grey

7.6

2½

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

{100}
perfect

3

The most common lead mineral; often occurs with sphalerite

Fe

Grey

Grey

7.8

4

Isometric; always massive

{100}
not prominent

6

Generally as meteorites, which always contain Ni; magnetic

NiAs

Copper-red

Brown-black

7.8

5½

Hexagonal; usually massive, compact or granular

None

2

Often coated with green annabergite

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

AuTe₂

Brass-yellow

Green-grey

9.3

2½

Monoclinic; bladed crystals or massive

None

1

Fuses easily on charcoal giving globules of Au

Bi

Silver-white, cream

Silver white

9.7-9.8

2½

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

{0001}
perfect

1

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

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

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

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

Formula

Colour

Streak

G

H

Habit

Cleavage

F

Observations

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

Brown to black

White to grey

4.1

6

Orthorhombic; tabular and prismatic crystals

None

7

Occurs as anatase

TiO₂

Red-brown

Yellow to grey

4.2-4.3

6½

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

{110}
imperfect

7

Common accessory mineral of igneous and metamorphic rocks

(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

FeTiO₃

Black

Black

4.6-4.8

6

Trigonal; tabular crystals; usually massive, compact or granular

None
parting on
{0001}
{011’2}

7

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

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

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

FeS₂

Light brass-yellow

Grey-black

4.88

6½

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

{101}
imperfect

3

Occurs in low temperature surface and near surface deposits

FeS₂

Light brass-yellow

Brown-black

5.0

6½

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

None

3

The most common sulphide mineral; alters to limonite

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

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

(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

Fe₂O₃

Red to black

Red-brown

5.26

6

Trigonal; tabular crystals and massive

None
parting on
{0001}
{011’2}

7

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

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

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

(Co,Ni)As_3-x

Silver-white

Black

6.5

6½

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

{100}
{111}
imperfect

3

Occurs in vein deposits; sometimes coated with pink erythrite

UO₂

Black

Brown-black

8-10

6½

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

PtAs₂

Silver-white

Black

10.6

6½

Isometric; cubic crystals and rounded grains

{001}
imperfect

2

Occurs in basic igneous rock and in sands produced from them

Formula

Colour

G

H

Habit

Cleavage

F

Observations

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

NaNO₃

Colourless, white

2.25

2

Trigonal; usually in granular masses

{1011’1}
perfect

1

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

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

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

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

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

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

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

Formula

Colour

G

H

Habit

Cleavage

F

Observations

KMgCl₃ · 6H₂O

Colourless or white

1.60

2½

Orthorhombic; usually in coarsely granular masses

None

1

Bitter taste, occurs in salt deposits; deliquescent

Na₂B₄O₅(OH)₄ · 8H₂O

White

1.71

2½

Monoclinic; short prismatic crystals

{100}
indistinct

1

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

Na₂B₄O₇ · 4H₂O

Colourless

1.91

2½

Monoclinic; massive, large cleavages

{100}
perfect
{001}
good

1

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

KCl

Colourless, sometimes white or grey

1.99

2½

Isometric; cubic crystals; usually massive, granular

{100}
perfect

2

Salty taste like halite, but somewhat bitter, sectile

SiO₂ · _nH₂O

Colourless, white

2.0 - 2.2

5 -5½

Amorphous; massive compact, sometimes mamillary

None

7

Secondary silica deposited at low temperatures

CaAl₂Si₄O₁₂ · 6H₂O

Colourless, white, pink

2.1

4

Trigonal; usually in cube-like rhombohedral crystals

{101’1}
perfect

3

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

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

NaCl

Colourless, white, red

2.16

2½

Isometric; cubic crystals; usually massive, granular

{100}
perfect

2

Characteristic salty taste

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

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

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

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

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

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

CaB₃O₄(OH)₃ · H₂O

Colourless, white

2.42

4½

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

{010}
perfect
{001}
imperfect

2

Occurs as geode-like masses in sedimentary rocks

CaCO₃

Colourless, white

2.71

3

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

{101’1}
perfect

7

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

CaMg(CO₃)₂

White, yellow, pink

2.85

3½ - 4

Trigonal; small curved rhombohedral crystals; also massive, granular

{101’1}
perfect

7

Effervesces in warm dilute HCl

KAl₃(SO₄)₂(OH)₆

White, pink

2.6 – 2.9

3½-4

Trigonal; usually massive, granular or compact

{0001}
perfect

7`

Often occurs in hydrothermal alteration of volcanic rocks

KAl₂(AlSi₃O₁₀)(OH)₂

Colourless or pale tints

2.8-2.9

2½-3

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

{001}
perfect

2

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

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

CaSiO₃

White

2.9

5

Triclinic; usually in columnar or fibrous masses

{100}
perfect
{1’02}
{001}
good

4

Occurs in metamorphosed limestones

CaCO₃

White

2.93

3½-4

Orthorhombic; hexagonal twinned crystals; also massive, sometimes coralloid

{010}
imperfect

7

Effervesces in cold dilute HCl; much less common than calcite

Na₃AlF₆

White

2.96

2½

Monoclinic; usually massive, coarsely granular

None
parting on
{001}
{110}

2

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

CaSO₄

White, grey, pale blue

3.0

3½

Orthorhombic; usually massive, granular

{010}
perfect
{100}{001}
good

3

Forms extensive belts in sedimentary rocks, alters to gypsum

MgCO₃

White

3.0

4

Trigonal; usually massive, compact

{101’1}
perfect

7

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

ALO(OH)

White, yellow, brown

3.0-3.1

3

Orthorhombic; always massive, compact; often pisolitic

{010}
not visible

7

Important constituent of bauxite

LiAlPO₄(OH)₂ · H₂O

White

3.1

5½

Triclinic; usually in cleavable masses

{100}
perfect;
{110}{01’1}
distinct

2

Often shows twinning striations on cleavages; occurs in granite pegmatites

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

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

SrCO₃

White

3.78

3½

Orthorhombic; usually massive, columnar to fibrous

{110}
good

6

Red flame colouration; effervesces in cold dilute HCl

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

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

ZnCO₃

White, yellow, blue, green

4.4

4

Trigonal; usually massive compact, often concretionary

{101’1}
good

7

Effervesces in warm dilute HCl

BaSO₄

Colourless, white, grey

4.5

3

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

{001}
{210}
perfect

3

Green flame colouration

CaWO₄

White, yellow, brown

6.1

5

Tetragonal; usually massive, granular

{101}
distinct

5

Fluoresces white or yellow in ultra violet light

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

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

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

Formula

Colour

G

H

Habit

Cleavage

F

Observations

SiO₂

Colourless, white

2.26

6½

Hexagonal; small thin hexagonal plates, often twinned

{101’0}
imperfect

7

Occurs in cavities in volcanic rocks

SiO₂

White

2.32

6½

Isometric; minute octahedra or small rounded aggregates

None

7

Occurs as isolated crystals in basic volcanic rocks

KalSi₂O₆

White, grey

2.45

6

Isometric; trapezohedral crystals

{110}
imperfect

7

Occurs as isolated crystals in volcanic rocks

NaAlSiO₄

White, brown, grey

2.5 – 2.6

6

Hexagonal; hexagonal prisms, and massive granular

{101’0}
imperfect

4

Gelatinises in HCl

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

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

(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

(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

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

(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

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

Ca(OH)BSiO₄

Colourless, pale yellow, pale green, white

3.0

6½

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

None

2

Occurs in cavities in basic igneous rocks associated with zeolites

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

LiAlSi₂O₆

Colourless, white, pink

3.1 – 3.2

6½

Monoclinic; long prismatic crystals, also platy masses

{110}
perfect
parting on {100}

4

Red flame colouration; occurs in granite pegmatites

Al₂SiO₅

White, grey, pink, brown

3.15

7½

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

Al₂SiO₅

White, brown, grey

3.24

7

Orthorhombic; usually in fibrous aggregates

{010}
perfect

7

Occurs in high grade schists and gneisses

AlO(OH)

White, grey, brown

3.3 - 3.4

6½

Orthorhombic; usually massive, bladed, foliated, or compact

{010}
perfect

7

Occurs in aluminium rich metamorphic rocks

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

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

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

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

Mg₃Si₄O₁₀(OH)₂ · xH₂O

Yellow, brown, green

2.4

1½

Monoclinic; pseudo-hexagonal plates, pseudomorphs after biotite

{001}
perfect

7

Expands enormously when heated; occurs in magnesium rich rocks

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

(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

Fe₃(PO₄)₂ · 8H₂O

Blue, blue-green

2.7

1½

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

Co₃(AsO₄)₂ · 8H₂O

Carmine-red

3.06

1½

Monoclinic; prismatic crystals and powdery masses

{010}
perfect

3

Streak pink, occurs as coatings or crusts on cobalt arsenides

· 10-12H₂O

Lemon-yellow

3.1 – 3.2

2 – 2½

Tetragonal; thin tabular on {001}; scaly aggregates

{001}
perfect

3

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

· 8-12H₂O

Emerald-green to apple-green

3.2 – 3.7

2 – 2½

Tetragonal; tabular on {001}; foliated or micaceous

{001}
perfect

3

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

As₂S₃

Yellow

3.48

1½

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

{001}
perfect

1

Streak yellow; often occurs with realgar

AsS

Red

3.56

2

Monoclinic; short prismatic crystals; usually in granular masses

{010}
distinct

1

Streak orange; often occurs with orpiment

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

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

AgCl

Colourless, yellow, grey

5.6

2

Isometric; usually massive, wax-like

None

1

Sectile; occurs in oxidised zone of silver deposits

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

S

Yellow

2.07

2½

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

CuSO₄ · 5H₂O

Blue

2.28

2½

Triclinic; short prismatic crystals; also massive, granular

{11’0}

3

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

CuSiO₃ · 2H₂O

Blue, green

2.4

2½ - 4

Orthorhombic (?); always massive, compact

None

7

Secondary mineral in oxidised copper ores

Mg₆Si₄O₁₀(OH)₈

Green, yellow, brown, grey

2.5 – 2.6

2½

Monoclinic; always massive, compact or fibrous (asbestos)

None visible

7

Alteration product of ultrabasic igneous rocks

(Mg,Ni)₆Si₄O₁₀(OH)₈

Apple-green

2.5 – 2.6

2½

Monoclinic; always massive, often as porous crusts

None visible

7

A nickel bearing serpentine

KLi₂Al(Si₄O₁₀)(OH)₂

Colourless, mauve, grey

2.8 – 2.9

2½ - 3

Monoclinic; usually massive, course to fine granular

{001}
perfect

2

Pale mauve colour often diagnostic; occurs in granite pegmatites

KMg₃(AlSi₃O₁₀)(OH)₂

Pale brown

2.8 – 2.9

2½ - 3

Monoclinic; usually in irregular platy crystals

{001}
perfect

4

Occurs in ultrabasic rocks and metamorphosed dolomites

(OH)₂

Green, brown, black

2.9 – 3.4

2½

Monoclinic; usually in irregular platy crystals

{001}
perfect

3

Occurs in acid igneous rocks, pegmatites, and metamorphic rocks

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

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

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)

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

MnCO₃

Pink

3.7

3½ - 4

Trigonal; usually massive, granular

{101’1}
perfect

7

Effervesces in warm dilute HCl; occurs in ore deposits

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

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

FeCO₃

Yellow, brown

3.8 – 4.0

4

Trigonal; rhombohedral aggregates, also massive, granular to compact

{101’1}
perfect

5

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

Cu₃(SO₄)(OH)₄

Dark green

3.88

3½

Orthorhombic; usually in granular masses or cross fibre veinlets

{010}
perfect

4

Streak green; soluble in HCl without effervescence

ZnS

Brownish-black

4.09

3½ - 4

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

{112’0}
distinct

6

Streak brown; much less common than 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

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

Cu₂(CO₃)(OH)₂

Green

4.0

4

Monoclinic; usually massive compact, often stalactitic or botryoidal

{2’01}
perfect

3

Streak green; effervesces in cold dilute HCl

HFeO₂

Yellow, brown

4.2

3 -5½

Orthorhombic; usually massive, compact or earthy, also stalactitic

{010}
perfect

6

Streak yellow; dissolves in dilute HCl giving a yellow solution

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

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

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

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

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.

PbCrO₄

Orange-red

6.1

3

Monoclinic; usually in prismatic crystals

{110}
imperfect

2

Streak orange-yellow; rare secondary mineral in lead veins

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

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

PbMoO₄

Yellow, red, brown

6.5 – 7.0

3

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

{010}
distinct

2

Often associated with vanadinite

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

HgS

Red

8.1

2½

Hexagonal; usually massive, granular

{101’0}
perfect

1

Streak red, volatises on heating

Formula

Colour

G

H

System & Habit

Cleavage

F

Observations

Na₈(AlSiO₄)₆Cl₂

Blue, white, pink

2.3

6

Isometric; usually massive, granular

{110}
perfect

4

Blue colour characteristic; occurs in nepheline syenites

Na₈(AlSiO₄)₆

Yellow, white, pink

2.4 – 2.5

6

Hexagonal; usually massive, granular

{101’0}
perfect

2

Effervesces in warm dilute HCl; its yellow colour often characteristic

(Mg,Fe)₂Al₄Si₅O₁₈

Colourless, blue, grey, brown

2.55 – 2.75

7

Orthorhombic; usually massive, granular

{010}
perfect

5

Occurs in aluminous metamorphic rocks

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

Be₃Al₂Si₆O₁₈

Colourless, white, green, yellow, blue

2.65 – 2.85

8

Hexagonal; prismatic crystals or massive, granular

{0001}
imperfect

5

Occurs in granite pegmatites

Si₃O₁₂OH

Black, dark brown

2.7 – 4.0

6½

Monoclinic; platy or columnar crystals, also massive, granular

{001}
seldom observable

3

Streak grey or green grey; often somewhat radioactive

CaAl₂Si₃O₁₀(OH)₂

White, pale green

2.9

6½

Orthorhombic; generally massive, encrusting with crystalline surface

{001}
not prominent

2

Occurs in cavities in basic igneous rocks associated with zeolites

Na,Mg,Fe,Al borosilicate

Black, brown, pink, green, blue

3.0 – 3.4

7½

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

None

6

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

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

(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

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

(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

(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

(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)

(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

Ca(Mg,Fe)Si₂O₆

White, green

3.25 – 3.40

6

Monoclinic; prismatic crystals, usually massive, granular

{110}
good

4

Occurs in metamorphosed dolomites

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

NaAlSi₂O₆

White, green

3.3

6½

Monoclinic; usually massive, granular to compact

{110}
good

3

Metamorphic mineral often associated with serpentine

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

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

(Mg,Fe)₂SiO₄

Olive-green

3.3 – 3.6

6½

Orthorhombic; usually massive, granular

{010}
imperfect

7

Occurs in basic and ultrabasic igneous rocks

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

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

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

(Mg,Fe)SiO₃

Brown, black

3.4 – 4.0

6

Orthorhombic; usually massive, platy

{210}
good

4

Occurs in basic igneous rocks

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

MnSiO₃

Pink

3.5 – 3.7

6

Triclinic; tabular crystals; usually massive, granular to compact

{110}
{11’0}
good

3

Often veined with black manganese oxides

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

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

Ca₃Al₂Si₃O₁₂

White, yellow, pink, brown

3.6 – 3.7

7

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

None