Orthopyroxene

Orthopyroxene crystal structure, CrystalMaker.

Orthopyroxene chemical variability. Enstatite (common in mafic rocks) always has high Mg and low Ca.

Formula

(Mg,Fe)₂Si₂O₆

Structure

Chain silicate

Crystal System

Crystal system: orthorhombic (+) (-)

Physical Properties

Colour in hand specimen: black
Cleavage: two at 90°
Hardness: 5-6

Optical Properties

Colour in plane polarised light: colourless, reddish or greenish
Pleochroism: variable weak to strong
Relief: moderate
Birefringence: 0.007-0.020; 1^st order grey to 2^nd order purple
Extinction: straight

Advanced Notes

Orthopyroxene has two end-member compositions: enstatite, Mg₂Si₂O₆, and ferrosilite, Fe²⁺₂Si₂O₆.

Mineral Name

orthopyroxene