Phlogopite
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
Plane-Polarized Light
- Similar to biotite but much lighter in color
- Occurrence is a strong clue: mostly mostly found in metamorphosed calc-silicate or ultramafic rocks.
Crossed Polarizers
- Similar to muscovite; the light coloration has little effect on the bright second and third-order interference colors.
The light tan mica in this plane-polarized view is phlogopite. It is lighter than biotite and mostly found in metamorphosed calc-silicate or ultramafic rocks.
In crossed polarizers (below) the light color has little effect on the bright second and third-order interference colors.
In calc-silicate metamorphic rocks it is possible to have talc, chlorite and phlogopite all in the same rock, creating the problem of sorting out three micaceous minerals. In the plane-polarized view below, the phlogopite is tan, the chlorite is light green and the talc is clear.
In crossed polarizers (below) the talc and phlogopite show bright interference colorswhile the chlorite has low first-order colors.
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Created 22 Sept 1997, Last Update