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Mica, Biotite

Mica, Biotite

This is one of the mica minerals common in the sand from the Palm Desert area. This grain has a 2V of about 0 degrees.

Transmitted Circular Polarized Light


Biotite is a sheet silicate with the general chemical composition indicated as
K2(Mg,Fe2+)6-4(Fe3+,Al,Ti) 0-2[(Si6-5Al2-3)O20](OH,F)4. It is a very common mineral.

Significance in the Environment:

Characteristic Features:

Biotite is dark green or Brown most often in thin section, has a 2V of 0-15 degrees, a birefringence of about 0.001 when view normal to its perfect cleavage plane, and has a negative optical sign. Biotite is the more iron-rich part of the phlogopite-biotite series. With more titanium the crystal becomes more reddish.

Associated Particles:


Deer, W. A., R. A. Howie, and J. Zussman, AN INTRODCUTION TO THE ROCK-FORMING MINERALS, ISBN 0-582-30094-0, pp. 298-307, 1992.