Sulfate minerals

name colour lustre Mohs hardness specific gravity

alum colourless; white vitreous 2–2½ 1.8

alunite white; grayish, yellowish, reddish, reddish brown vitreous 3½–4 2.6–2.9

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 bluish or violet vitreous to pearly 3½ 3.0

antlerite emerald to blackish 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

brochantite emerald to blackish 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

chalcanthite various shades of blue vitreous 2½ 2.3

coquimbite pale violet to deep purple vitreous 2½ 2.1

epsomite colourless; aggregates are white vitreous; 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, brownish, yellowish (massive) subvitreous 2 (a hardness standard) 2.3

halotrichite colourless to white vitreous 1.5 1.7 (pick) to 1.9 (halo)

jarosite ochre yellow to dark brown subadamantine to vitreous; resinous on fracture 2½–3½ 2.9–3.3

kainite colourless; gray, blue, violet, yellowish, reddish vitreous 2½–3 2.2

kieserite colourless; grayish white, yellowish vitreous 3.5 2.6

linarite deep azure blue vitreous to subadamantine 2.5 5.3

mirabilite colourless to white vitreous 1½–2 1.5

plumbojarosite golden brown to dark brown dull to glistening or silky soft 3.7

polyhalite colourless; white or gray; often salmon pink from included iron oxide vitreous to resinous 3.5 2.8

thenardite colourless; reddish, grayish, yellowish, or yellow brown vitreous to resinous 2½–3 2.7

name habit fracture or cleavage refractive 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 compact massive; tabular or prismatic crystals one good, one distinct cleavage alpha = 1.868–1.913

beta = 1.873–1.918

gamma = 1.884–1.931 orthorhombic

anhydrite granular or fibrous massive; concretionary (tripestone) two perfect, one good cleavage alpha = 1.567–1.580

beta = 1.572–1.586

gamma = 1.610–1.625 orthorhombic

antlerite thick tabular crystals one perfect cleavage alpha = 1.726

beta = 1.738

gamma = 1.789 orthorhombic

barite usually in tabular crystals; rosettes (desert roses); massive one perfect, one good cleavage alpha = 1.633–1.648

beta = 1.634–1.649

gamma = 1.645–1.661 orthorhombic

botryogen reniform, botryoidal, or globular aggregates one perfect, one good cleavage alpha = 1.523

beta = 1.530

gamma = 1.582 monoclinic

brochantite prismatic to hairlike crystal and crystal aggregates; granular massive; crusts one perfect cleavage alpha = 1.728

beta = 1.771

gamma = 1.800 monoclinic

caledonite coating of small elongated crystals one perfect cleavage alpha = 1.815–1.821

beta = 1.863–1.869

gamma = 1.906–1.912 orthorhombic

celestite tabular crystals; fibrous massive one perfect, one good cleavage alpha = 1.618–1.632

beta = 1.620–1.634

gamma = 1.627–1.642 orthorhombic

chalcanthite short prismatic crystals; granular masses; stalactites and reniform masses conchoidal fracture alpha = 1.514

beta = 1.537

gamma = 1.543 triclinic

coquimbite prismatic and pyramidal crystals; granular massive omega = 1.536

epsilon = 1.572 hexagonal

epsomite fibrous or hairlike crusts; woolly efflorescences one perfect cleavage alpha = 1.430–1.440

beta = 1.452–1.462

gamma = 1.457–1.469 orthorhombic

glauberite tabular, dipyramidal, or prismatic crystals one perfect cleavage alpha = 1.515

beta = 1.535

gamma = 1.536 monoclinic

gypsum elongated tabular crystals (some 5 ft long; others twisted or bent); granular or fibrous masses; rosettes one perfect cleavage alpha = 1.515–1.523

beta = 1.516–1.526

gamma = 1.524–1.532 monoclinic

halotrichite aggregates of hairlike crystals conchoidal fracture alpha = 1.475–1.480

beta = 1.480–1.486

gamma = 1.483–1.490 monoclinic

jarosite minute crystals; crusts; granular or fibrous massive one distinct cleavage omega = 1.82

epsilon = 1.715 hexagonal

kainite granular massive; crystalline coatings one perfect cleavage alpha = 1.494

beta = 1.505

gamma = 1.516 monoclinic

kieserite granular massive, intergrown with other salts two perfect cleavages alpha = 1.520

beta = 1.533

gamma = 1.584 monoclinic

linarite elongated tabular crystals, either singly or in groups one perfect cleavage; conchoidal fracture alpha = 1.809

beta = 1.839

gamma = 1.859 monoclinic

mirabilite short prisms; lathlike or tabular crystals; crusts or fibrous masses; granular massive one perfect cleavage alpha = 1.391–1.397

beta = 1.393–1.410

gamma = 1.395–1.411 monoclinic

plumbojarosite crusts, lumps, compact masses of microscopic hexagonal plates one fair cleavage omega = 1.875

epsilon = 1.786 hexagonal

polyhalite fibrous to foliated massive one perfect cleavage alpha = 1.547

beta = 1.560

gamma = 1.567 triclinic

thenardite rather large crystals; crusts, efflorescences one perfect, one fair cleavage alpha = 1.464–1.471

beta = 1.473–1.477

gamma = 1.481–1.485 orthorhombic