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Chemical Formula | NaAlSi3O8 | ||
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Composition | Sodium aluminum silicate, often with the
sodium partially replaced by calcium or potassium. If calcium replaces more than 10 percent of the sodium, the mineral is not Albite, but a different member of the Plagioclase Feldspar group. If potassium replaces more than 10 percent of the sodium, the mineral is not Albite, but Anorthoclase. |
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Variable Formula | (Na,Ca)AlSi3O8 (Na,K)AlSi3O8 |
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Color | White, colorless, cream, light yellow, light blue, light green, pale red, light brown, gray. Some Albite is iridescent. | ||
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Streak | White | ||
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Hardness | 6 - 6½ | ||
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Crystal Forms and Aggregates |
(Triclinic) Crystals are usually flat and bladed, and often in compact groupings. Also
occurs as tall prismatic and short, stubby, tabular crystals. These crystals are usually in
groupings, and rarely occur singly on a matrix. Crystal twins are common. Other forms are grainy, massive, columnar, and rosette. Crystals are sometimes striated. |
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Transparency | Transparent to translucent | ||
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Specific Gravity | 2.6 - 2.63 | ||
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Luster | Vitreous to pearly | ||
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Cleavage | 2,1 - basal ; 2,1 - prismatic ; 3,1 -
pinacoidal The cleavage angle is about 90º |
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Fracture | Conchoidal to uneven | ||
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Tenacity | Brittle | ||
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Other Names |  White Feldspar, Soda
Feldspar, Sodaclase |
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Varieties |  Clevelandite - Thin, bladed crystals or plates of Albite Pericline
- Elongated, white prismatic crystals of Albite Peristerite
- Iridescent variety of Albite Analbite
- Albite containing a small percentage of potassium
replacing the sodium. The ratio of sodium to potassium
must be greater than 9:1, otherwise the mineral is Anorthoclase.See also Perthite |
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In Group | Silicates ; Tectosilicates ; Feldspar group ; Plagioclase Feldspars | ||
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All About | Albite 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. 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 is an important rock-forming mineral. It takes a longer time for Albite to crystallize than the other feldspars. This enables Albite to form near-perfect crystals. Albite is a common accessory mineral to rare and unusual minerals. The iridescent variety Peristerite sometimes exhibits an adularescent sheen. This produces an unusual form of Moonstone. |
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Uses | Albite is industrially important in the manufacture of ceramics. Albite provides the best crystallized examples of Plagioclase feldspars, and these crystals are popular among collectors. Albite is also important in the study of mineral environments and crystal formations. | ||
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Striking Features | Crystal habits, cleavage, hardness, and color | ||
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Complex Tests | Soluble in hydrofluoric acid | ||
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Popularity (1-4) | 2 | ||
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Prevalence (1-3) | 1 | ||
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Demand (1-3) | 1 | ||
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Distinguishing Similar Minerals |
Potassium feldspars - don't exhibit striations on twinned crystal surfaces, whereas the
Plagioclase feldspars usually do Other Plagioclase Feldspars - usually cannot be determined by practical means Spodumene - has a splintery cleavage Calcite - much softer (3) |
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Commonly Occurs With |
Quartz, Muscovite, Biotite, Potassium Feldspar, Tourmaline, Hornblende | ||
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Noteworthy Localities |
Albite is a common mineral, but localities
where fine Albite crystals can be found are limited. Some
excellent examples have come from the Swiss Alps and the
Tyrol, Austria. Enormous Clevelandite crystals have come
from several areas in Minas Gerais, Brazil. In Canada,
Albite is found in the Francon quarry, near Montreal, and
Mount St.-Hilaire, Quebec. In the U.S., some of the best and clearest crystals are from Amelia Court House, Amelia Co., Virginia. Other localities are Pala, San Diego Co., California; the Little Three mine, Ramona, San Diego Co., California; the Foote Spodumene mine, Kings Mt., Cleveland Co., North Carolina; and Auburn, Androscoggin Co., Maine. |
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Picture Icon Links |
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Picture Links | 1. Albite variety Cleavlandite |
