Microcline

Plane-Polarized Light

• Low relief
• Clear
• Cleavage often visible (A)
• Usually numerous inclusions, giving it a much dustier look than quartz. The inclusions are due to microscopic alteration (B)

Crossed Polarizers

• Gray to white interference colors, slightly lower than quartz
• Alteration products often have high interference colors (A)
• Often has a distinctive crosshatch or "tartan" twinning pattern.(B)
• Perthitic texture, due to exsolution of plagioclase, is very common (C). It is easily visible in hand specimen as irregular milky streaks.

Quartz, the feldspars, cordierite and nepheline all have low relief and gray to white interference colors. Beginners find them hard to tell apart. View Quartz and its Look-Alikes.

The photo below shows tartan twinning clearly.

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Created 22 Sept 1997, Last Update 20 May 2002

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