Talc

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

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Plane-Polarized Light

• Low relief
• Clear
• Perfect micaceous cleavage

Crossed Polarizers

• Bright second-and third-order interference colors
• Essentially indistinguishable from muscovite
• Best clue to identity is occurrence: talc is most likely to occur in calc-silicate and other magnesium-rich rocks. The sketch above shows a groundmass of calcite and quartz.

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Below is a mass of chlorite and talc. The talc is visible in plane polarized light by a slight color difference, perhaps due to a tiny amount of iron.

In crossed polars the chlorite has very low interference colors while the talc has bright second order colors.

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Created 16 December 1999, Last Update

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