Dolomite (thin section)

Key Characteristics: Relief which changes upon rotation of stage, extreme δ, rhombohedral cleavage and lamellar twinning are all diagnostic. Dolomite usually has higher refractive indices than calcite and may be colorless or iron stained where calcite is generally colorless. 2V: n/a Relief: Low negative to high positive relief; Relief changes upon stage rotation Cleavage: Perfect rhombohedral cleavage Colour and Plechroism: Colorless in thin section, weathered or altered samples may appear brown or iron stained due to iron oxides Optical Orientation: Symmetrical or inclined extinction Twinning: Lamellar twinning common Optical character: Uniaxial (-)