Satin spar
Satin spar, less commonly atlas spar, is a trivial, partly obsolete name for fibrous varieties of the minerals gypsum, calcite, and aragonite. Satin spars have a characteristic satin luster. Despite their very low hardness, satin spars are widely used as ornamental stones.
Spar is a general term for glassy, transparent to translucent minerals that cleave easily. Satin spars are not related to other minerals containing spar in their names, such as feldspar and fluorspar.
Main minerals and varieties
Satin spar gypsum is a white, fibrous variety of gypsum that is sometimes called selenite.Satin spar calcite, or calcite spar, is a fibrous variety of calcite that superficially resembles satin spar gypsum, but is much less common in nature.- Aragonite is one of the polymorphic varieties of calcite, sometimes having the same satin effect.