The plagioclase feldspar andesine

	Chemical Formula	(Na,Ca)Al_1-2Si_3-2O₈
	Composition	Sodium calcium aluminum silicate. The ratio of sodium to calcium is about 7:3. The amount of aluminum atoms are between 1 and 2, and the amount of silicon atoms are between 3 and 2. In the Plagioclase Feldspar series, Andesine contains between 50 and 70 percent Albite (Ab), and between 30 and 50 percent Anorthite (An).
	Color	Colorless, white, cream, yellow, pale green, gray
	Streak	White
	Hardness	6 - 6½
	Crystal Forms and Aggregates	(Triclinic) Crystals, which are uncommon, are tabular and frequently twinned. Most commonly occurs massive, grainy, as chunky masses, and as compact crystal groupings.
	Transparency	Transparent to translucent
	Specific Gravity	2.66 - 2.68
	Luster	Vitreous to pearly
	Cleavage	2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal The cleavage angle is about 90º
	Fracture	Conchoidal to uneven
	Tenacity	Brittle
	In Group	Silicates ; Tectosilicates ; Feldspar group ; Plagioclase Feldspars
	All About	Andesine belongs to the Plagioclase Feldspar group, an isomorphous solid solution series. Albite is one end member, containing sodium and no calcium. The other end member, Anorthite, contains calcium and no sodium. The intermediary members are Oligoclase, Andesine, Labradorite, and Bytownite.
	Uses	Andesine, as a common Plagioclase Feldspar, is industrially important in the manufacture of ceramics.
	Striking Features	Crystal habits, cleavage, and hardness
	Popularity (1-4)	2
	Prevalence (1-3)	1
	Demand (1-3)	2
	Distinguishing Similar Minerals	Potassium feldspars - don't exhibit striations on twinned crystal surfaces, whereas the Plagioclase feldspars do Other Plagioclase Feldspars - usually cannot be determined by practical means Spodumene - has a splintery cleavage Calcite - much softer (3)
	Commonly Occurs With	Quartz, Muscovite, Biotite, Hornblende, Potassium Feldspar
	Noteworthy Localities	Andesine is prevalent in volcanic regions throughout the world. It is named after Andes Mountains, in the locality of Marmato, Bolivia. Large crystals are found in the San Gabriel Mountains of California.
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