Birds eye extinction tutorial Optical Mineralogy
Channel: Matt Kohn
Date: 2021-05-03

Explanation of what birds' eye extinction (BEE) is, the most common minerals that show BEE, and one rare species of mica that does not show BEE. Supported by Boise State University and the US National Science Foundation.
Key characteristic: "pebbly texture" in cross-polars, especially when most of the grain is extinct
00:00 Birds' eye maple banjo
00:19 Close-up of birds' eye maple banjo resonator
00:48 Coarse igneous muscovite
01:18 Biotite
01:49 Biotite with dense BEE
02:19 Talc
02:52 Clintonite [Ca(Fe,Mg)3Al2Si2O10(OH)2] = mica without BEE