Rhombic
High-birefringence

Description

Transparent colorless. Nonpleochroic. Extremely high birefringence. Equant cleavage rhombs, usually with sharp edges. High relief. Usually detrital but may be authigenic in some rare environments. Usually small (fine silt to clay) grains. Higher relief than calcite, and rhombs generally more equant than calcite, but can be difficult to conclusively distinguish from calcite.

Imposters

Difficult to distinguish between calcite and dolomite. Dolomite rhombs are typically more equant and higher relief, with sharper cleavage edges.

External Resources

Dolomite on MinDat