K-feldspar tutorial Optical mineralogy

Several videos of K-feldspar 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 plane-polarized 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

[@zuakaa]

You are an amazing teacher. I really appreciate your work. Thank you!

[@WhatDuhDogDoin]

Could you do another video covering typical orthoclase which is a lot more common?

[@mattkohn7819]

I'll see what I can do. Actually, I don't have a lot of rocks with orthoclase, but I can search our collections and tap my colleagues.

[@WhatDuhDogDoin]

@@mattkohn7819that would be really appreciated! I’ve found most k-spar that isn’t microcline or perthitic to be annoying to differentiate from quartz when the cleavage isn’t obvious

[@импактиты]

Микроклин это!