Optical properties

Carbonates can easily be distinguished in thin sections of the soil as they have a white interference colour of higher order (with yellowish and light brown tones).

They are colourless (the large crystals being transparent but normally looking greyish).

Depending upon there orientation they can have both a moderate positive or negative relief.

They are generally massive or granular, sometimes scalenohedral, prismatic or needle-shaped.

They have perfect cleavage according to the faces of the rhombohedron.

They may show polysynthetic twinning.

The carbonate which usually forms in the soil is calcite:

uniaxial

and negative.

 

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