Description
The mineral glaucophane is a sodium-magnesium-aluminum inosilicate with the chemical formula Na2Mg3Al2(Si8O22)(OH)2. It belongs to the amphiboles. The translucent gray, blue, or blue-black glaucophane has a gray-blue streak color, a vitreous to pearlescent luster, and good cleavage along the crystal faces [110] and [001]. Its average density is 3.07 and its hardness is 6 to 6.5. The crystal system is monoclinic, and the mineral is not radioactive. The name of the mineral glaucophane is derived from the Greek words glaucos ("blue") and phanos ("to appear," "to shine"). Glaucophane is a very common mineral in igneous and metamorphic rocks. It is one of the most common amphiboles and a typical mineral for the metamorphic blueschist facies.
