CaAl 2 Si 2 O 8 Composition Calcium aluminum silicate. May contain some sodium replacing the calcium, but that amount must be less than 10 percent.
Crystals are prismatic or tabular , and are usually twinned .
Also occurs grainy and massive . Transparency Transparent to translucent Specific Gravity 2.74 - 2.76 Luster Vitreous. 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 .