Carbonates

Calcite

Calcite group.
Hexagonal.
Prismatic, rhombohedral, scalenohedral, fine-grained, compact, earthy, stalactitic.
H = 3 on cleavage, 2.5 on base
SG = 2.71
Transparent to translucent.
Color = white, colorless (Iceland Spar), tinted with gray, red, green, blue, yellow, brown, black.
Effervesce in cold HCl.

Magnesite

Calcite group.
Hexagonal.
Cryptocrystalline in white, compact, earthy masses; coarse to fine.
H = 3.5-5
SG = 3-3.2
Vitreous luster.
Transparent to translucent.
Color = white, gray, yellow, brown.
Derived from Mg-rich igneous rocks.

Siderite

Calcite group.
Hexagonal.
Granular, botryoidal, compact, earthy.
H = 3.5-4
SG = 3.96
Vitreous luster.
Transparent to translucent.
Color = light to dark brown.
Soluble to hot HCl.
Chalybite.
Spherosiderite is concretionary variety.

Rhodochrosite

Calcite group.
Hexagonal.
Cleavable, massive, granular, compact.
H = 3.5-4
SG = 3.5-3.7
Vitreous luster.
Transparent to translucent.
Color = shade of rose-red, light pink, dark brown.
Streak = white.
Soluble in hot HCl.

Kutnahorite [CaMn(CO3)2]

Substitution product of Ca and Mn.
Similar with rhodochrosite.

Smithsonite

Calcite group.
Hexagonal.
Reniform, botryoidal, stalactitic, incrustations, granular to earthy.
Dry-bone ore.
H = 4-4.5
SG = 4.3-4.45
Vitreous luster.
Transparent to translucent.
Color = usually dark brown, colorless, white, green, blue, pink, yellow (turkey-fat ore).
Soluble in cold HCl.
Supergene.

Hydrozincite

Secondary mineral in Zn deposits.
Same specie as smithsonite.

Aragonite

Aragonite group.
Orthorhombic.
Acicular pyramidal, tabular, reniform, columnar, stalactitic.
H = 3.5-4
SG = 2.94
Vitreous luster.
Transparent to translucent.
Color = white, colorless, pale yellow, variously tinted.
Effervesce in cold HCl.
Less common than calcite.

Barytocalcite [BaCa(CO3)2]

Analogous to dolomite but the constituents are Ca and Ba.

Witherite

Aragonite group.
Orthorhombic.
Deeply striated horizontally, botryoidal, globular, columnar, granular.
H = 3.5
SG = 4.31
Vitreous luster.
Translucent.
Color = white, colorless, gray.
Effervesce in cold HCl.
Rare, associated with galena.

Strontianite

Aragonite group.
Orthorhombic.
Acicular, radiating, columnar, fibrous, granular.
H = 3.5-4
SG = 3.78
Vitreous luster.
Transparent to translucent.
Color = white, gray, yellow, green.
Effervesce in HCl.
Low T hydrothermal mineral.

Cerussite

Aragonite group.
Orthorhombic.
Tabular, reticulated, granular crystalline, fibrous, compact, earthy.
H = 3-3.5
SG = 6.58
Adamantine luster.
Transparent to translucent.
Color = white, gray, colorless.
Effervesce in nitric acid.
Supergene ore formed by the action of carbonated waters on galena.

Phosgenite (Pb2CO3Cl2)

Rare.
Tetragonal.
Similar specie with cerussite.

Dolomite

Dolomite group.
Hexagonal.
Saddle-shaped, coarse, granular, fine-grained, compact.
H = 3.5-4
SG = 2.85
Vitreous (pearl spar) luster.
Transparent to translucent.
Color = colorless, white, green, gray, brown, black, flesh-pink.
Effervesce in hot HCl.

Ankerite

Dolomite group.
Hexagonal.
Does not occur in well-formed crystals.
H = 3.5-4
SG = 2.85
Vitreous (pearl spar) luster.
Transparent to translucent.
Color = yellowish-white, yellowish-brown (due to oxidation of Fe).
Common in Precambrian Fe-formations.

Kutnahorite [CaMn(CO3)2]

Isostructural with dolomite.

Malachite

Monoclinic.
Slender prismatic, radiating, botryoidal, stalactitic, granular, earthy.
H = 3.5-4
SG = 3.9-4.03
Adamantine-vitreous (crystals), silky (fibrous), dull (earthy) luster.
Translucent.
Color = bright green.
Streak = pale green.
Soluble in HCl.
Supergene Cu.

Azurite

Monoclinic.
Malformed, radiating, spherical.
H = 3.5-4
SG = 3.77
Vitreous luster.
Transparent to translucent.
Color = intense azure-blue.
Effervesce in HCl.
Less common than malachite.

Aurichalcite [(Zn,Cu)5(CO3)2(OH)3]

Orthorhombic.
Acicular.
Pale green to blue.

Gaylussite [Na2Ca(CO3)2 . 5H2O]

Monoclinic.
Found in saline lake deposits.
Similar specie with malachite and azurite.

Trona [Na3(CO3)(HCO3) . 2H2O]

Monoclinic.
Found in saline lake deposits.
Similar specie with malachite and azurite.