"Positive and negative extinction angles in the feldspars." -Johannsen, 1908

Extinction Angles

"Positive and negative extinction angles in the feldspars." -Johannsen, 1908

"Extinction angles on the (001) faces of the lime-soda feldspars." -Johannsen, 1908

Extinction Angles

"Extinction angles on the (001) faces of the lime-soda feldspars." -Johannsen, 1908

"Extinction angles on the (010) faces of the lime-soda feldspars." -Johannsen, 1908

Extinction Angles

"Extinction angles on the (010) faces of the lime-soda feldspars." -Johannsen, 1908

"The (010) plane of an orthoclase crystal." -Johannsen, 1908

Orthoclase Crystal

"The (010) plane of an orthoclase crystal." -Johannsen, 1908

"The (001) plane of an orthoclase crystal." -Johannsen, 1908

Orthoclase Crystal

"The (001) plane of an orthoclase crystal." -Johannsen, 1908

A simple orthoclase crystal.

Orthoclase Crystal

A simple orthoclase crystal.

A simple orthoclase crystal.

Orthoclase Crystal

A simple orthoclase crystal.

A simple orthoclase crystal.

Orthoclase Crystal

A simple orthoclase crystal.

"Simple orthoclase crystal showing cleavage lines and the position of the twinning plane in a Carlsbad twin." -Johannsen, 1908

Orthoclase Crystal

"Simple orthoclase crystal showing cleavage lines and the position of the twinning plane in a Carlsbad…

"Simple orthoclase crystal opened out to show the optical orientation." -Johannsen, 1908

Orthoclase Crystal

"Simple orthoclase crystal opened out to show the optical orientation." -Johannsen, 1908

"A Carlsbad twin of orthoclase." -Johannsen, 1908

Orthoclase Twin

"A Carlsbad twin of orthoclase." -Johannsen, 1908

"A Baveno twin of orthoclase." -Johannsen, 1908

Orthoclase Twin

"A Baveno twin of orthoclase." -Johannsen, 1908

"A (010) cleavage flake of plagioclase." -Johannsen, 1908

Plagioclase

"A (010) cleavage flake of plagioclase." -Johannsen, 1908

"The (010) face of a Carlsbad twin of plagioclase." -Johannsen, 1908

Plagioclase Twin

"The (010) face of a Carlsbad twin of plagioclase." -Johannsen, 1908

"Albite and Carlsbad twinning combined." -Johannsen, 1908

Twinning

"Albite and Carlsbad twinning combined." -Johannsen, 1908