Sugilite triple A Kalahari Desert South Africa rough chunks

The mineral sugilite is a potassium-sodium-iron-manganese-aluminum lithium silicate having the chemical formula KNa2 (Fe2 +, Mn2 +, Al) 2 Li3 Si12 O30. The mineral belongs to the cyclosilicates. The translucent to translucent brown, pink or purple sugilite has a glass gloss, a white stripe color and the cleavage is unclear according to the crystal plane. The average density is 2.74 and the hardness is 6 to 6.5. The crystal system is hexagonal and the radioactivity of the mineral is hardly measurable. The 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 mainly in metamorphic manganese-containing rocks and in alkaline solidification rocks. The type location is located on the Iwagi island in the Ehime Prefecture, Japan.