Dolomite

related topics
{acid, form, water}
{island, water, area}
{disease, patient, cell}
{food, make, wine}
{math, energy, light}
{specie, animal, plant}

Dolomite (pronounced /ˈdɒləmaɪt/) is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate CaMg(CO3)2 found in crystals.

Dolomite rock (also dolostone) is composed predominantly of the mineral dolomite. Limestone that is partially replaced by dolomite is referred to as dolomitic limestone, or in old U.S. geologic literature as magnesian limestone. Dolomite was first described in 1791 as the rock by the French naturalist and geologist, Déodat Gratet de Dolomieu (1750–1801) for exposures in what are now known as the Dolomite Alps of northern Italy.

Contents

Properties

The mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, gray to pink, commonly curved crystals, although it is usually massive. It has physical properties similar to those of the mineral calcite, but does not rapidly dissolve or effervesce (fizz) in dilute hydrochloric acid unless it is scratched or in powdered form. The Mohs hardness is 3.5 to 4 and the specific gravity is 2.85. Refractive index values are nω = 1.679 - 1.681 and nε = 1.500. Crystal twinning is common. A solid solution series exists between dolomite and iron rich ankerite. Small amounts of iron in the structure give the crystals a yellow to brown tint. Manganese substitutes in the structure also up to about three percent MnO. A high manganese content gives the crystals a rosy pink color noted in the image above. A series with the manganese rich kutnohorite may exist. Lead and zinc also substitute in the structure for magnesium.

Formation

Vast deposits are present in the geological record, but the mineral is relatively rare in modern environments. Laboratory synthesis of stoichiometric dolomite has been carried out only at temperatures of greater than 100 degrees Celsius (conditions typical of burial in sedimentary basins), even though much dolomite in the rock record appears to have formed in low-temperature conditions. The high temperature is likely to speed up the movement of calcium and magnesium ions so that they can find their places in the ordered structure within a reasonable amount of time. This suggests that the lack of dolomite that is being formed today is likely due to kinetic factors. I.e. due to the lack of kinetic energy or temperature.

Full article ▸

related documents
Gallium
Tertiary structure
Californium
Standard electrode potential (data page)
Ununtrium
Indium
Coenzyme Q - cytochrome c reductase
Neodymium
Ethylene glycol
Toluene
Gel electrophoresis
Nucleotide
Erbium
Tartaric acid
Eutectic point
Oxidation state
Pyridine
Ribosome
Island of stability
Americium
Isoprene
Protease
Primer (molecular biology)
Extractive metallurgy
Cellulose
Organelle
Filtration
Fluorite
Radionuclide
Kaolinite