KAlSi₃O₈

Microcline is a silicate of potassium and aluminum with the composition KAlSi₃O₈ . The sample above is about 60x40 cm and is from Keyhole vug, Crystal Peak, Florissant, Colorado. It is described as microcline with albite. The section at right shows more detail of the structure of both minerals.

Microcline is classified as a feldspar.

This microcline sample is labeled Carlsbad twinned crystal and is from Crystal Peak, Colorado. It is about 8x8 cm.

This sample is described as spessartine with helvite, quartz, and microcline. It is about 20 cm long and is from Tongbei, Fujian Province, China. The black crystals are taken to be microcline, the orange spessartine, and the tan helvite. The black crystals show the crystal form of microcline, but the black color is unusual. It is confusing, since there is a black sample of spessartine on display as well, and a white sample of microcline with aquamarine.

This specimen is smoky quartz in a bed of microcline. The sample is about 15cm wide and is from Crystal Peak, Colorado.