Nitrates, Borates, Sulfates, and Chromates

Nitratite

Hexagonal.
H = 1-2
SG = 2.29
Soluble in water.
Isostructural with calcite.

Niter

Orthorhombic.
Saltpeter.
Fuses easily, soluble in water.
Less common that nitratite.
Isostructural with aragonite.

Kernite

Monoclinic.
Coarse, long, splintery, cleavable aggregates.
H = 3
SG = 1.95
Vitreous to pearly luster.
Color = colorless to white.
Colorless varieties become chalky white on long exposure to air because of tincalconite.
Slowly soluble in water.
Formed by recrystallization of borax.
Locality in Mojave Desert.

Borax

Monoclinic.
Massive, cellular or incrustations.
H = 2-2.5
SG = 1.7
Vitreous luster.
Translucent.
Color = colorless to white.
Sweetish-alkaline taste.
Clear crystals effloresce and turn to white with formation of tincalconite.
Soluble in water.

Ulexite

Triclinic.
Rounded masses of loose texture, fine fibers of acicular or capillary crystals, cotton-balls, television rock.
H = 2.5
SG = 1.96
Silky luster.
Tasteless.
Color = white.
Forms in arid regions.

Colemanite

Monoclinic.
Short prismatic, massive, granular, compact.
H = 4-4.5
SG = 2.42
Vitreous luster.
Transparent to translucent.
Color = colorless to white.

Boracite (Mg3ClB7O13)
Hydroboracite [CaMgB6O8(OH)6 . 3H2O]
Inyoite [CaB3O3(OH)5 . 4H2O]

Other locally abundant borates.

Sinhalite [Mg(Al,Fe)BO4]

Rare borate gem mineral.
Found in gravels of Sri Lanka and Burma.
Misidentified as brown peridots.

Barite

Barite group.
Orthorhombic.
Diamond-shaped, divergent, tabular (crested barite or barite roses), coarsely laminated, granular, earthy.
H = 3-3.5
SG = 4.5
Vitreous to pearly (on base) luster.
Transparent to translucent.
Color = colorless, white, light shades of blue, yellow, red.
Gangue in hydrothermal veins, associated with Ag, Pb, Cu, Co, Mn, and Sn.
Used as heavy mud in drilling.

Lithopone

A white pigment of barium sulfate and zinc sulfide.

Historical Note: Lithopone was once a primary substitute for lead carbonate or "white lead" pigments; it has been largely replaced by titanium dioxide.

Celestite

Barite group.
Orthorhombic.
Barite-like, elongated parallel, radiating, fibrous, granular.
H = 3-3.5
SG = 3.95-3.97
Vitreous to pearly luster.
Transparent to translucent.
Color = colorless, white, tainted with faint blue or red.

Anglesite

Barite group.
Orthorhombic.
Prismatic parallel, massive, granular, compact, earthy concentric layers.
H = 3-3.5
SG = 4.5
Conchoidal fracture.
Adamantine (crystalline), dull (earthy) luster.
Transparent to translucent.
Color = colorless, white, gray, pale shades of yellow.
Associated with galena.

Anhydrite

Barite group.
Orthorhombic.
Massive or in crystalline masses, fibrous, granular, massive.
H = 3-3.5
SG = 2.89-2.98
Vitreous to pearly (on cleavage) luster.
Color = colorless, bluish, violet, white, rose, brown, red.

Crocoite

Chromate.
Monoclinic.
Slender prismatic, vertically striated, columnar, granular.
H = 2.5-3
SG = 5.9-6.1
Adamantine luster.
Translucent.
Color = bright hyacinth-red.
Streak = orange-yellow.
Isostructural with monazite.
Rare, Cr was first discovered here.

Gypsum

Monoclinic
Tabular, diamond-shaped, swallowtail twins.
H = 2
SG = 2.32
Fibrous fracture.
Conchoidal surface.
Vitreous, pearly, silky luster.
Transparent to translucent.
Color = colorless, white, gray, shades of yellow, brown, red.
Most common sulfate.

Satin spar

Is a fibrous variety of gypsum with a pearly luster.

Alabaster

A white or delicately tinted fine-grained, massive gypsum.

Desert rose

Desert Rose is a crystalline form of either gypsum.
Both of these minerals are soft and can be scratched with your fingernail.

Selenite

Is a form of gypsum occurring as transparent crystals, sometimes in thin plates.

Antlerite

Orthorhombic.
Slender prismatic, vertically striated, parallel aggregates, reniform, massive.
H = 3.5-4
SG = 3.9
Vitreous luster.
Transparent to translucent.
Color = emerald to blackish-green.
Streak = pale green.
Main ore of Chuquicamata.

Brochantite [Cu4SO4(OH6)]

More widespread than antlerite.
Have the same properties as antlerite.
Considered as chief ore of Chuquicamata until 1925.
Green.

Chalcanthite (CuSO4 . 5H2O)

Hydrous copper sulfate.
Abundant in Chuquicamata.
Blue vitriole.

Epsomite (MgSO4 . 7H2O)

Occurs as efflorescent mineral on rocks in mine workings and in cave walls.

Melanterite (FeSO4 . 7H2O)

Secondary mineral found as an efflorescence on mine timbers.
White, disintegration product of marcasite.

Alunite

Hexagonal.
Tabular, massive, disseminated.
H = 4
SG = 2.6-2.8
Vitreous-pearly (crystals), earthy (massive) luster.
Transparent to translucent.
Color = white, gray, reddish.
Difficult to distinguish from limestone/dolostone.
Alumstone.
Formed by H2SO4 acting on K-feldspar-rich rocks.

Natroalunite [(Na,K)Al3(SO4)2(OH)6

Formed when Na exceeds K in the chemical formula of alunite.

Jarosite [KFe3(SO4)2(OH)6]

Fe3+ analogue of alunite.
Found as crusts or coatings on ferruginous ores.