Rafferty J.P. (ed.) Minerals

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7 Minerals 7

292

name colour lustre Mohs’

hard-

ness

specific

gravity

monazite yellowish brown

or reddish brown

to brown

usually resin-

ous or waxy;

sometimes

vitreous or

adamantine

5–5½ 4.6–5.4;

usually

5.0–5.2

pyromor-

phite

olive green; yel-

low; gray; brown

to orange

resinous to

subadaman-

tine

3½–4 7.0

torbernite various shades of

green

vitreous to

subadaman-

tine

2–2½ 3.2

triphylite bluish or

greenish gray

(triphylite); clove

brown, honey

yellow, or salmon

(lithiophilite)

vitreous to

subresinous

4–5 3.3–3.6 not

varying

linearly

with com-

position

triplite dark brown;

ﬂesh red; salmon

pink

vitreous to

resinous

5–5½ 3.5–3.9

turquoise blue to various

shades of green;

greenish to yel-

lowish gray

waxy 5–6 2.6–2.8

variscite yellowish green,

pale to emerald

green, bluish

green or colour-

less (variscite);

peach-blossom

red, carmine,

violet (strengite)

vitreous to

faintly waxy

3½–4½ 2.2–2.5

293

carbonates and other Minerals 7

name colour lustre Mohs’

hard-

ness

specific

gravity

vivianite colourless when

fresh, darkening

to deep blue or

bluish black

vitreous 1½–2 2.7

wavellite greenish white;

green to yellow

vitreous 3½–4 2.4

xenotime yellowish brown

to reddish brown;

ﬂesh red, grayish

white, pale yel-

low, or greenish

vitreous 4–5 4.4–5.1

phOSphATe MINerAlS

name habit or

form

frac

ture or

cleavage

refrac-

tive

indices

crystal

system

amblygo-

nite

large, trans-

lucent,

cleavable

masses; small

transparent

crystals

one perfect

and one

good

cleavage

ambl mont

alpha =

1.578–1.611

beta =

1.595–1.619

gamma =

1.598–1.633

triclinic

apatite

carbonate-

apatite

prismatic or

thick tabu-

lar crystals;

coarse

granular to

compact mas-

sive; nodular

concretions

conchoidal

to uneven

fracture

n = 1.63–1.67 hexagonal

7 Minerals 7

294

name habit or

form

frac-

ture or

cleavage

refrac-

tive

indices

crystal

system

chlorapatite

ﬂuorapatite

hydroxyl-

apatite

autunite thin tabular

crystals; ﬂaky

aggregates;

crusts

one

perfect,

micalike

cleavage

alpha = 1.553

beta = 1.575

gamma = 1.577

tetragonal

brushite transpar-

ent to

translucent

efﬂorescences

or minute

crystals

two perfect

cleavages

alpha = 1.539

beta = 1.546

gamma = 1.551

mono-

clinic

collophane

(massive

apatite)

crypto-

crystalline

massive;

hornlike con-

cretions and

nodules

n = 1.59–1.61

lazulite crystals;

compact

masses;

grains

two

cleavages;

uneven to

splintery

fracture

lazul scorz

alpha =

1.604–1.639

beta =

1.626–1.670

gamma =

1.637–1.680

mono-

clinic

monazite translu-

cent, small

ﬂattened

crystals

one

distinct

cleavage

alpha =

1.79–1.80

beta = 1.79–1.80

gamma =

1.84–1.85

mono-

clinic

295

name habit or

form

frac-

ture or

cleavage

refrac-

tive

indices

crystal

system

pyromor-

phite

barrel-

shaped

prisms;

globular,

kidney-shaped,

or grape-like

masses

uneven to

subcon-

choidal

fracture

epsilon =

2.030–2.031

omega =

2.041–2.144

hexagonal

torbernite tabular crys-

tals; micalike

masses

one per-

fect, platy

cleavage

epsilon = 1.582

omega = 1.592

tetragonal

triphylite transpar-

ent to

translucent

cleavable

or compact

massive

one perfect

cleavage

triph lith

alpha =

1.694–1.669

beta =

1.695–1.673

gamma =

1.700–1.682

ortho-

rhombic

triplite massive one good

cleavage

alpha =

1.643–1.696

beta =

1.647–1.704

gamma =

1.668–1.713

mono-

clinic

turquoise opaque,

dense, cryp-

tocrystalline

to ﬁne granu-

lar massive

one perfect

and one

good

cleavage

alpha = 1.61

beta = 1.62

gamma = 1.65

triclinic

7 carbonates and other Minerals 7

7 Minerals 7

296

name habit or

form

frac-

ture or

cleavage

refrac-

tive

indices

crystal

system

variscite ﬁne-grained,

round or

grapelike

aggregates,

nodules,

veins, or

crusts

one good

cleavage

varis stren

alpha =

1.563–1.707

beta =

1.588–1.719

gamma =

1.594–1.741

ortho-

rhombic

vivianite rounded

prismatic

crystals;

kidney-shaped,

tubelike,

or globu-

lar masses;

concretions

one perfect

cleavage

alpha =

1.579–1.616

beta =

1.602–1.656

gamma =

1.629–1.675

mono-

clinic

wavellite translucent,

hemispherical,

or globular

aggregates

one perfect

and one

good

cleavage

alpha =

1.520–1.535

beta =

1.526–1.543

gamma =

1.545–1.561

ortho-

rhombic

xenotime small pris-

matic crystals;

coarse radial

aggregates;

rosettes

uneven to

splintery

fracture

epsilon =

1.816–1.827

omega =

1.721–1.720

tetragonal

Sulfate Minerals

These minerals are naturally occurring salts of sulfuric

acid. About 200 distinct kinds of sulfates are recorded in

mineralogical literature, but most of them are of rare and

local occurrence. Abundant deposits of sulfate minerals,

297

carbonates and other Minerals 7

such as barite and celestite, are exploited for the prepa-

ration of metal salts. Many beds of sulfate minerals are

mined for fertilizer and salt preparations, and beds of pure

gypsum are mined for the preparation of plaster of paris.

All sulfates possess an atomic structure based on dis-

crete insular sulfate (SO

) tetrahedra, i.e., ions in which

four oxygen atoms are symmetrically distributed at the

corners of a tetrahedron with the sulfur atom in the cen-

tre. These tetrahedral groups do not polymerize, and the

sulfate group behaves as a single negatively charged mol-

ecule, or complex. Thus, sulfates are distinct from the

silicates and borates, which link together into chains,

rings, sheets, or frameworks.

Sulfate minerals can be found in at least four kinds:

as late oxidation products of preexisting sulﬁde ores, as

evaporite deposits, in circulatory solutions, and in depos-

its formed by hot water or volcanic gases. Many sulfate

minerals occur as basic hydrates of iron, cobalt, nickel,

zinc, and copper at or near the source of preexisting pri-

mary sulﬁdes. The sulﬁde minerals, through exposure

to weathering and circulating water, have undergone

oxidation in which the sulﬁde ion is converted to sul-

fate and the metal ion also is changed to some higher

valence state. Noteworthy beds of such oxidation prod-

ucts occur in desert regions, such as Chuquicamata,

Chile, where brightly coloured basic copper and ferric

iron sulfates have accumulated. The sulfate anions gener-

ated by oxidation processes may also react with calcium

carbonate rocks to form gypsum, CaSO

∙2H

O. Sulfates

formed by the oxidation of primary sulﬁdes include ant-

lerite [Cu

(SO

)(OH)

], brochantite [Cu

(SO

)(OH)

chalcanthite [Cu

(SO

)∙5H

O], anglesite (PbSO

), and

plumbojarosite [PbFe

(SO

)

(OH)

Soluble alkali and alkaline-earth sulfates crystal-

lize upon evaporation of sulfate-rich brines and trapped

7 Minerals 7

298

oceanic salt solutions. Such brines can form economically

important deposits of sulfate, halide, and borate minerals

in thick parallel beds, as the potash deposits at Stassfurt,

Ger., and the southwestern United States. Many of the

sulfate minerals are salts of more than one metal, such as

polyhalite, which is a combination of potassium, calcium,

and magnesium sulfates.

Sulfate minerals common in evaporite deposits

include anhydrite, gypsum, thenardite (Na

), epso-

mite (MgSO

∙7H

O), glauberite [Na

Ca(SO

)

], kainite

(MgSO

∙KCl∙3H

O), kieserite (MgSO

∙H

O), mirabilite

(Na

∙10H

O), and polyhalite [K

Mg(SO

)

∙2H

O].

Groundwater carrying sulfate anions reacts with cal-

cium ions in muds, clays, and limestones to form beds of

gypsum. The massive material is called alabaster or plaster

of paris (originally found in the clays and muds of the Paris

basin). If such beds become deeply buried or metamor-

phosed (altered by heat and pressure), anhydrite may form

by dehydration of the gypsum.

Numerous sulfates, usually simple, are formed directly

from hot aqueous solutions associated with fumarolic

(volcanic gas) vents and late-stage ﬁssure systems in ore

deposits. Noteworthy examples include anhydrite, barite,

and celestine.

SulfATe MINerAlS

name colour lustre M

ohs

hard-

ness

specific

gravity

alum colourless; white vitreous 2–2½ 1.8

alunite white; grayish,

yellowish, reddish,

reddish brown

vitreous 3½–4 2.6–2.9

299

name colour lustre Mohs

hard-

ness

specific

gravity

alunogen white; yellowish

or reddish

vitreous to

silky

1½–2 1.8

anglesite colourless to

white; often

tinted gray, yellow,

green, or blue

adamantine

to resinous

or vitreous

2½–3 6.4

anhydrite colourless to blu-

ish or violet

vitreous to

pearly

3½ 3.0

antlerite emerald to black-

ish green; light

green

vitreous 3½ 3.9

barite colourless to

white; also

variable

vitreous to

resinous

3–3½ 4.5

botryogen light to dark

orange red

vitreous 2–2½ 2.1

brochan-

tite

emerald to black-

ish green; light

green

vitreous 3½–4 4.0

caledonite deep verdigris

green or bluish

green

resinous 2½–3 5.8

celestite pale blue; white,

reddish, greenish,

brownish

vitreous 3–3½ 4.0

chal-

canthite

various shades of

blue

vitreous 2½ 2.3

coquim-

bite

pale violet to deep

purple

vitreous 2½ 2.1

7 carbonates and other Minerals 7

7 Minerals 7

300

name colour lustre Mohs

hard-

ness

specific

gravity

epsomite colourless; aggre-

gates are white

vitre-

ous; silky

to earthy

(ﬁbrous)

2–2½ 1.7

glauberite gray; yellowish vitreous to

slightly waxy

2½–3 2.75–2.85

gypsum colourless; white,

gray, brown-

ish, yellowish

(massive)

subvitreous 2 (a

hard-

ness

stan-

dard)

2.3

halotrich-

ite

colourless to

white

vitreous 1.5 1.7 (pick) to

1.9 (halo)

jarosite ochre yellow to

dark brown

suba-

damantine

to vitreous;

resinous on

fracture

2½–3½ 2.9–3.3

kainite colourless; gray,

blue, violet, yel-

lowish, reddish

vitreous 2½–3 2.2

kieserite colourless; grayish

white, yellowish

vitreous 3.5 2.6

linarite deep azure blue vitreous to

subadaman-

tine

2.5 5.3

mirabilite colourless to

white

vitreous 1½–2 1.5

plumbo-

jarosite

golden brown to

dark brown

dull to glis-

tening or silky

soft 3.7

301

carbonates and other Minerals 7

name colour lustre Mohs

hard-

ness

specific

gravity

polyhalite colourless; white or

gray; often salmon

pink from included

iron oxide

vitreous to

resinous

3.5 2.8

thenardite colourless; red-

dish, grayish,

yellowish, or yel-

low brown

vitreous to

resinous

2½–3 2.7

SulfATe MINerAlS

name habit frac

ture or

cleavage

refrac-

tive

indices

crystal

system

alum columnar or

granular massive

conchoidal

fracture

n = 1.453–1.466 isometric

alunite granular to

dense massive

conchoidal

fracture

omega = 1.572

epsilon = 1.592

hexagonal

alunogen ﬁbrous masses

and crusts

one perfect

cleavage

alpha =

1.459–1.475

beta =

1.461–1.478

gamma =

1.884–1.931

triclinic

anglesite granular to com-

pact massive;

tabular or pris-

matic crystals

one good,

one

distinct

cleavage

alpha =

1.868–1.913

beta =

1.873–1.918

gamma =

1.884–1.931

ortho-

rhombic