In this case the rock consists for more than 90% of dolomite and less than 10% of calcite.Dolomite 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 magnesian limestone. Vast deposits are present in the geological record, but the mineral is relatively rare in modern environments.
However, 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 kinematic factors.