Albite
Albite is the sodium-rich end-member of the plagioclase feldspar series, with the formula NaAlSi3O8, forming a continuous solid-solution series with the calcium end-member anorthite. It typically appears as white, cream, or pale gray tabular crystals with two cleavage directions meeting near a right angle. Its low density and glassy luster set it apart from denser silicates, and it is a defining component of many granites, gneisses, and pegmatites.
Albite properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | NaAlSi3O8 |
| Mohs hardness | 6–6.5 |
| Crystal system | Triclinic |
| Luster | Vitreous, pearly on cleavage |
| Streak | White |
| Cleavage | Perfect on {001}, good on {010}, near 86° angle |
| Fracture | Uneven to conchoidal |
| Specific gravity | 2.60–2.65 |
| Transparency | Transparent to translucent |
| Common colors | White, Colorless, Gray, Greenish, Pale blue (rare) |
| Rarity | common |
Geology & background
Albite crystallizes from silica-rich magmas and also grows during regional metamorphism of sodium-bearing rocks, where it commonly forms porphyroblasts in schist and appears as a low-temperature alteration product of calcium-rich plagioclase, a process called albitization. It is a rock-forming mineral present in granite, syenite, and countless pegmatites, and it frequently occurs as the striated, gray-white variety cleavelandite lining pegmatite pockets. Fine specimens with visible polysynthetic twinning come from pegmatites in Brazil and Madagascar, and moonstone-quality albite-orthoclase intergrowths are mined in Sri Lanka and southern India.
For collectors, albite is valued less for rarity than for the elegant striations visible on cleavage faces, a feature that helps separate plagioclase from potassium feldspar out in the field. Because it functions mainly as a rock-forming mineral rather than a standalone gem, specimen prices stay modest except for gemmy peristerite or moonstone material. Rockhounds should watch for confusion with microcline and orthoclase, since these feldspars overlap heavily in hardness, color, and general appearance.
How to identify Albite
Look for a white to pale gray or bluish mineral with a vitreous, sometimes pearly luster on cleavage surfaces and a white streak. Two cleavage directions intersect at nearly 90 degrees, and a hardness of about 6 lets it scratch glass but not quartz. The best diagnostic is fine parallel striping on one cleavage face, produced by polysynthetic twinning, which separates albite from striation-free orthoclase. It is frequently mistaken for microcline, quartz, and other feldspars within massive granite.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Albite is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Albite worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- The gem variety peristerite, a layered intergrowth of albite and oligoclase, produces a bluish schiller effect prized in jewelry.
- Albite's name traces back to the Latin albus, meaning white, a nod to its typical pale coloring.
- Repeated twinning inside albite crystals can be so fine that it produces the silky sheen seen in moonstone.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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