Description
The mineral sugilite is a potassium-sodium-iron-manganese-aluminum-lithium silicate with the chemical formula KNa2(Fe2+,Mn2+,Al)2Li3Si12O30. The mineral belongs to the cyclosilicates. Transparent to translucent brownish-yellow, pink, or purple sugilite has a vitreous luster, a white streak color, and indistinct cleavage according to the crystal plane [0001]. The average density is 2.74 and the hardness is 6 to 6.5. The crystal system is hexagonal, and the mineral's radioactivity is barely measurable. Its gamma ray value, according to the American Petroleum Institute, is 54.07. The mineral sugilite is named after the Japanese petrologist Ken-ichi Sugi (1901–1948). Sugilite occurs primarily in metamorphic manganese-bearing rocks and in alkali-rich igneous rocks. The type locality is located on Iwagi Islet in Ehime Prefecture, Japan.
