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"A positive biaxial interference figure with the principal sections nearly corresponding to those of the nicols. The arrows indicate the movement taking place upon inserting a quartz wedge above the section." -Johannsen, 1908

Biaxial Interference

"A positive biaxial interference figure with the principal sections nearly corresponding to those of…

"A biaxial interference figure showing the emergence of an optic axis. The arrow indicates the movement taking place upon inserting a quartz wedge above the section. The mineral is augite. (+)." -Johannsen, 1908

Biaxial Interference

"A biaxial interference figure showing the emergence of an optic axis. The arrow indicates the movement…