Oligoclase

Table of contents

1 Pronunciation 2 Noun 3 Chemical composition 4 Physical properties 5 Related words

Pronunciation

O lig' o klaze

Noun

1. A plagioclase feldspar, the second member of the Albite-Anorthite solid solution series. Primarily found as small crystals in impure marble. Oligoclase contains a small amount of calcium substituting for some of the sodium in its formula. Oligoclase with reddish-golden inclusions found in Norway and Canada is called sunstone.

Chemical composition

• Sodium calcium aluminum silicate, Failed to parse (PNG conversion failed; check for correct installation of latex, dvips, gs, and convert): Na_xCa_xAlSi_3O_8

Physical properties

• Moh's Hardness: 6.0
• Specific gravity: 2.65
• Color: white, yellow, reddish-gray
• Luster: glassy
• Fracture: conchoidal
• Cleavage: two good at about 94º to each other
• Habit: Triclinic - pinacoidal. Usually twinned and striated, but this may not be visible to the unaided eye.

Related words

See Rock, Feldspar, Plagioclase