CALCITE
Calcite is a common mineral. It is calcium
carbonate (CaCO3). It has a nonmetallic luster, commonly
clearish to whitish to yellowish to grayish in color, is moderately soft
(H≡3), moderately light-weight, has hexagonal crystals, and rhombohedral
cleavage (three cleavage planes at 75º & 105º angles - cleavage pieces look
like lopsided boxes). The easiest way to identify calcite is to drop acid
on it - it easily bubbles (effervesces) in acid. The bubbles are carbon
dioxide gas. If the acid is dilute hydrochloric acid, the chemical
reaction is:
2HCl(aq) + CaCO3(s) -->>
CO2(g)↑ + H2O(l) + CaCl2(aq)
The most important & voluminous calcitic rocks in
the world are limestone (sedimentary), marble (metamorphic), carbonatite
(igneous), and travertine (speleothem, or "cave formations",
and many hotspring deposits). Quite a few hydrothermal veins in the world
are calcitic or have calcite as a principal component.
Calcite
cleavage rhombs (both are 3.2 cm across)
Left:
optically clear calcite ("Iceland spar").
Right:
optically clear, pale pinkish calcite.
Calcite
- unbroken hexagonal crystal from the Cumberland Mine, Smith County, Tennessee,
USA.
Calcite
from Dalnegorsk, Maritime Province, eastern Russia. Specimen owned by
Terry Huizing.
Calcite
- unbroken crystals from Hubei Province, east-central China. Specimen
owned by Terry Huizing.
Calcite
from Guangdong Province, South China. Specimen owned by Terry Huizing.
Calcite
from cavities in Deccan Traps flood basalt (Cretaceous-Tertiary boundary, 65
m.y.), Jalgaon District, northern Maharashtra State, west-central India.
Specimens owned by Terry Huizing.
Calcite
- helictite from the Santa Eulalia Mining District in Chihuahua State, Mexico.
Calcite
on fluorite from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine,
Cave-in-Rock Mining District, southern Illinois, USA. Specimen owned by
Ross Lillie.
Calcite
from Yunnan Province, southwestern China. Specimen owned by Terry
Huizing.
Calcite "straws" from the Second Sovietskiy Mine, Dalnegorsk, Maritime
Province, eastern Russia (Dwyer Mercer County District Library # 200-125,
Celina, Ohio, USA).
Poker-chip calcite from Charcas, Mexico (Dwyer Mercer County District
Library # 222-450, Celina, Ohio, USA)
Calcite sand rose from Fontaineblue, north-central France (CSM # 53397,
Colorado School of Mines Geology Museum, Golden, Colorado, USA).
Calcite
from Aurangabad, India. Specimen owned by Terry Huizing.
Cobaltoan calcite (a.k.a. cobaltocalcite) (3.8 cm across) from
Shaba/Katanga Province, Zaire ("D.R. Congo"). Cobaltoan calcite
is a deep pinkish-purple variety of calcite having significant cobalt impurity
- (Ca,Co)CO3.
Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit
in the Second Sovietskiy Mine at Dalnegorsk, Maritime Province, eastern
Russia. Manganoan calcite is a pinkish calcite with significant manganese
impurity - (Ca,Mn)CO3.
Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit
at Dalnegorsk, Maritime Province, eastern Russia. Specimen owned by Terry
Huizing.
Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit
at the Huanzala Mine, Huallanca District, Dos de Mayo Province, Huánuco
Department, Peru. The skarn deposit is developed along a felsic dike that
has intruded limestones of the Lower Cretaceous Santa Formation. Specimen
owned by Terry Huizing.
Photo gallery of cobaltoan
calcite
Photo gallery of manganoan
calcite