Several videos of Kfeldspar in thin section, showing typical textures and optical characteristics. Supported by Boise State University and the US National Science Foundation.
Key characteristics: Relief very slightly lower than quartz (subtle), clear in planepolarized light, with no pleochroism, low interference colors (white), tartan twinning (microcline), perthite (albite exsolution), carlsbad twinning (sanidine), clay alteration (brown "staining").
00:00​ Typical microcline with tartan twinning
00:30​ More tartan twinning
01:00​ Slightly perthitic
01:31​ Strongly perthitic, clay alteration
02:01​ Beautiful perthite, clay alteration
02:31​ Sanidine