Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Plane-Polarized Light

High relief. Can occur as colorless irregular grains (A) or be tinted yellowish or greenish (B). Common alteration or metamorphic mineral derived from plagioclase, and small euhedral crystals in plagioclase are common (C).

Piemontite, an uncommon manganese-bearing epidote, is one of the showpieces of geology. It has a dazzling pleochroism in yellow, orange, red and magenta (D). It cannot be mistaken for anything else.

Crossed Polarizers

Moderately high birefringence resulting in vivid second- and third- order colors. Anomalous interference colors are common in the variety zoisite (A). Piemontite's bright colors totally dominate its interference colors.

The euhedral light-green crystals below, seen in plane-polarized light, are epidote. Note the rather high relief.

EPIDOTP1.JPG (78307 bytes)

Same field in crossed polarizers. The bright interference colors are typical.

EPIDOTX1.JPG (104154 bytes)

The brightly-colored mass in the center of this view in crossed polarizers is epidote. Variegated bright interference colors like these are typical of epidote.

EPIDOTX2.JPG (96331 bytes)

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Created 10 Oct 1997, Last Update 16 December 1999

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