Its crystals are usually not all that attractive, but some specimens are real standouts with well-formed crystals with a shiny black color and an opaque submetallic luster. Ilvaite is a member of the Sorosilicate subclass of the silicate minerals. Sorosilicates have an unusual basic unit of Si 2 O 7 . This group of atoms is composed of two silicate tetrahedrons that share one oxygen giving the group an hourglass shape. A fine specimen of ilvaite can be a valuable addition to anyones collection.
Color is normally black, but also brownish black to dark gray.
Luster is submetallic or resinous. Transparency crystals are opaque. Also as platy crystals and in massive, compact and columnar specimens. Cleavage very poor, in one direction lengthwise. Fracture is conchoidal.