Plagioclase tutorial optical mineralogy

Several videos of plagioclase in thin section, showing typical textures and optical characteristics. Supported by Boise State University and the US National Science Foundation.
Key characteristics: low relief, colorless, low interference colors (maximum = white), twinning or zoning
00:00 Two grains, one with twins, one without
00:30 Single zoned and twinned grain
01:00 Single grain both twinned and untwinned
01:30 An untwinned grain with twinned grains around it
02:00 Strongly zoned (and twinned)
02:30 Typical plagioclase in a granite
03:00 Bizarre metamorphosed amygdule
03:31 Volcanic interlocking grains
04:01 With melt inclusions
04:31 Albite and pericline twins