ALBITE - A member of the Plagioclase Feldspar group. 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.
CHEMISTRY: (Na,Ca)AlSi3O8
COLOR: Usually white (Albite is derived from the same root word as albino) or colorless but can be shades of cream, light yellow, light blue, light green, pale red, light brown, gray. Some Albite is iridescent. (see moonstone)
HARDNESS: 6 - 6.5
SPECIFIC GRAVITY: Approximately 2.61 (average) to 2.8
REFRACTIVE INDEX: 1.53
CLEAVAGE: Perfect in one and good in another direction forming nearly right-angled prisms.
FRACTURE: Conchoidal
CRYSTALLOGRAPHY: triclinic; bar 1
Crystal Habits include blocky, tabular and platy crystals. The typical crystal has a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. A variety called Cleavelandite forms very thin platy crystals that can grow rather large (15+ cm across) but can maintain an even thickness of only a few millimeters. Twinning is almost universal in albite. Crystals can be twinned according to the Albite, Carlsbad, Manebach and Baveno laws. Albite is a common constituent of granitic and syenite rocks. Can also be massive.
Streak is white.
Luster is vitreous to dull if weathered.
Transparency crystals are translucent to opaque and only sometimes transparent.
Other names: White Feldspar; Soda Feldspar; Sodaclase
Associated Minerals: Quartz, tourmaline, biotite, horneblend and muscovite.
Other Characteristics: 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.
Notable Occurrences include Labrador, Canada and the Scandinavian Peninsula.
Best Field Indicators are occurrence, crystal habit, twinning, striations, density and index of refraction.
Albite is a common felspar and is the "pivot" mineral of two different feldspar series. It is most often associated with the plagioclase series where it is an end member of this series. The plagioclase series comprises feldspars that range in chemical composition from pure NaAlSi3 O8 to pure CaAl2 Si2 O8 . The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements. Albite is also an end member of the alkali or K-feldspars whose series ranges from pure NaAlSi3 O8 to pure KAlSi3 O8. This series only exists at high temperatures with the mineral sanidine being the potassium, K-rich end member. At lower temperatures, the K-feldspars will separate from the albite in a process called exsolution. The albite will form layers inside the k-feldspars crystals.
Albite is the last of the feldspars to crystallize from molten rock. The process of crystallization from a molten rock body serves to isolate rarer elements in the last stages of crystallization and therefore produces rare mineral species. Thus albite is often found with some lovely rare and beautiful minerals. Although usually not an exceptional collection mineral in itself, albite can be a nice accessory mineral to other mineral species. A variety associated with tourmaline is called cleavelandite and forms extremely thin, platy, white and sometimes very transparent crystals.
Healing Properties:
- A stone which strengthens the lungs, spleen and thymus.
