any of a series of triclinic feldspars that form rocks
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.
Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite and anorthite. The albite:anorthite molar ratio ranges from 90:10 to 70:30. Oligoclase is a high sodium feldspar crystallizing in the triclinic system. The Mohs hardness is 6 to 6.5 and the specific gravity is 2.64 to 2.66. The refractive indices are: nα=1.533–1.543, nβ=1.537–1.548, and nγ=1.542–1.552. In color it is usually white, with shades of grey, green, or red.
Chambers 20th Century Dictionary
ol′i-gō-klās, n. a soda-lime triclinic feldspar.
The numerical value of oligoclase in Chaldean Numerology is: 9
The numerical value of oligoclase in Pythagorean Numerology is: 8
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