The Mineral albite

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.
Oligoclase and Andesine are considered by some to be a variety of
Albite rather then a separate mineral. The acclaimed Dana's System of
Mineralogy lists these intermediary members as individual minerals,
whereas the IMA does not recognize them as individual mineral species.

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 in
large and well crystallized examples. Albite is also a common accessory mineral to many rare and unusual minerals.

The iridescent variety Peristerite sometimes exhibits an adularescent sheen. This produces an unusual form of Moonstone.

Albite sometimes forms in association with the feldspar mineral Microcline in alternating patterns, and forms a
feldspar rock known as Perthite.

hemical Formula

NaAlSi₃O₈

Composition

Sodium aluminum silicate, often with the sodium partially replaced by calcium or potassium.

Color

White, colorless, cream, light yellow, light blue, light green, pale red, light brown, gray. Some Albite is iridescent with schillers.

Streak

White

Hardness

6 - 6.5

Crystal System

Triclinic

3D Crystal Atlas
(Click for animated model)

Crystal Forms
and Aggregates

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, rosette, and coxcomb.
Crystals are sometimes striated.

Click here
for more detailed information on the crystal structure of the
Feldspars.

Transparency

Transparent to translucent

Specific Gravity

2.6 - 2.63

Luster

Vitreous to pearly

Cleavage

2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. The cleavage angle is about 90º.

Fracture

Subconchoidal to uneven

Tenacity

Brittle

Complex Tests

Soluble in hydrofluoric acid

In Group

Silicates; Tectosilicates; Feldspar Group

Striking Features

Crystal habits, cleavage, hardness, and color

Environment

Most often in granite pegmatite, also in metamorphic rocks.

Popularity (1-4)

2

Prevalence (1-3)

1

Demand (1-3)

1

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The Mineral albite

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The Mineral albite

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