|
Orthoclase Family:
Tectosilicates (Potassium aluminum silicate, sometimes with considerable sodium) KAlSi3O8 AKA: Adularia, Amazonite, Amazonstone, Potash feldspar, Sanidine, Microcline, Moonstone |
|
System: Monoclinic (orthoclase, sanidine) or triclinic (microcline); predominantly as single crystals of rectangular or square cross section and as tabular crystals; twin crystals very common; also cleavage masses, granular, disseminated grains. Appearance: White, pink, brown, gray, green, colorless, yellowish; vitreous; streak white. Physical properties: Hardness: (6.0 - 6.5), Specific gravity: (2.5 - 2.6), Cleavage: Good in two directions at 90 degrees; fracture, uneven; transparent to translucent. Orthoclase, adularia, sanidine and microcline are the potash feldspars. Adularia is transparent or opalescent (moonstone); sanidine is glassy; and microcline is white to pale yellow, rarely red; when bright-green, microcline is called amazonstone. Similar species: Plagioclase feldspars show twinning striations in fresh cleavage surfaces; spodumene breaks with splintery fracture; other similar silicate minerals lack the right-angle cleavage. Occurrence: The potash feldspars are important rock-forming minerals in plutonic, volcanic and metamorphic rocks. Orthoclase commonly occurs in granite, and microcline in granite pegmatites, carbonatites and hornfels of contact metamorphic rocks. Aldularia and sanidine are usually found in volcanic rocks. Microcline is the potash feldspar that usually forms intergrowths with quartz (called "graphic granite") and with albite (called "perthite") in granite pegmatites. Miscellaneous: Orthoclase takes its name from the Greek orthos, "upright", and klasis, "fracture", in allusion to its two prominant cleavages at right angles to each other. The potash feldspars are used for gemstones and in ceramics. Conventional Wisdom: This mineral can help one to overcome tragedy, and can provide assistance in the alignment of the chakras. It emits an energy of liveliness and pleasantness, stimulating tact, finesse, poise and refinement. It is also helpful in providing remedial action for behavioral disorders. Belongs to the Astrological Sign of Cancer. |