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The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae known as Bøggild intergrowth. The specific gravity in the plagioclase series increases from albite (2.62) to anorthite (2.72–2.75).
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. [1]
Specific gravity: 2.64–2.66: ... Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance.
Buddingtonite has a hardness of 5.5 and a specific gravity of 2.32. Buddingtonite was discovered in 1964 at the Sulfur Bank mine near Clear Lake in Lake County, California. [6] Clear Lake is at the north end of The Geysers geothermal area. It also occurs in the Tonopah, Nevada [7] area and in hydrothermal areas in New Zealand [8] and Japan.
Specific gravity: 2.55–2.63: Optical properties: ... It is a type of potassium feldspar, also known as K-feldspar. The gem known as moonstone (see below) ...
Specific gravity: 2.54–2.66: Optical properties: ... A solid solution of the plagioclase feldspar oligoclase +/− the potassium feldspar orthoclase also produces ...
Albite is a plagioclase feldspar mineral. ... pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 to 6.5.
Specific gravity: 2.72–2.75: Optical properties: ... Anorthite (an = not, ortho = straight) is the calcium endmember of the plagioclase feldspar mineral series.