The composition of albite is Na[AlSi3O8]. It is a plagioclase with a triclinic crystal system. The crystals appear as bladed blocks, and crystal twinning is common. It can sometimes appear as block, granular or flaky aggregates. Thin slices are often curved. The colour is generally white or colourless, and can also be light blue, grey, green or pale red with white streaks. It has transparent to translucent diaphaneity, a vitreous or pearly lustre, a specific gravity of 2.60–2.63, a Mohs hardness of 6–6.5 and uneven fractures. It is a main component of several magmatic rocks, such as granite, rhyolite, andesite and syenite. Albite can also form in metamorphic rocks, such as schist and gneiss, and certain sedimentary rocks. It can also be found in hydrothermal veins.