The chemical compound name is potassium aluminium silicate, and it is known as E number reference E555.

It is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase.

Microcline is identical to orthoclase in many physical properties, and can be distinguished by x-ray or optical examination.

When viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable.

The Spanish explorers who named it apparently confused it with another green mineral from that region.