Albite
General Information
Albite belongs to the Plagioclase Feldspar group, an isomorphous solid solution series. It 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.
Albite also forms a series with Sanidine, and the intermediary member of this series is Anorthoclase. Albite can contain up to ten percent potassium replacing the sodium. If more than ten percent replaces the sodium, the mineral is no longer Albite, but Anorthoclase.
Albite is a very common mineral and an important rock-forming mineral. It takes a longer time for Albite to crystallize than the other feldspars. This enables it to form near-perfect crystals. It is a common accessory mineral to rare and unusual minerals.
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Chemistry: NaAlSi3O8, Sodium Aluminum Silicate
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Class: Silicates
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Subclass: Tectosilicates
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Color: White or colorless; can be blue, yellow, orange, or brown
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Streak: White |
Luster: Vitreous to dull
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Transparency: Transparent to Opaque
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Crystal System: Triclinic
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Hardness: 6-6.5
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Cleavage: Perfect in one direction; good in another
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Fracture: Conchoidial
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Specific Gravity: Approximately 2.61
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Crystal Habits: Blocky, tabular, and platy crystals. Crystals typically square or rectangle. Often forms twins. Can be massive |
Uses: Ceramics, ornamental stone, mineral specimens
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Associated Minerals: Quartz, Tourmaline, Muscovite
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Other Characteristics: Index of refraction is 1.53. Lamellar twinning may cause a grooved effect on cystal surfaces that appear as striations. Some albite may show an opalescence due to twinning and is referred to as moonstone
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Notable Occurrences: Labrador, Canada; Scandinavian Peninsula
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Best Field Indicators: Crystal habit, twinning, striations, density and index of refraction
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