Nambulite

Nambulite is a lithium bearing manganese silicate mineral with the chemical formula (Li,Na)Mn4Si5O14(OH). It is named after the mineralogist Matsuo Nambu (born 1917) of Tohoko University, Japan, who studies manganese minerals. It was first discovered in the Funakozawa Mine of northeastern Japan in a metasedimentary manganese ore. Nambulite is formed from the reaction between a hydrothermal solution and rhodonite, and commonly creates veins in the host rock. It has little economic value other than as a collector's gem. It belongs to the triclinic-pinacoidal crystal system (or triclinic-normal), meaning that it has three axes of unequal length (a, b, c), all intersecting at oblique angles with each other (none of the angles are equal to 90°). It belongs to the crystal class 1, meaning that any point on the crystal that is rotated 360° and then completely inverted will meet with an equal (but opposite) point on the crystal (see centrosymmetry). Its space group is P 1. The three axes (a, b, c) have different indices of refraction, na = 1.707, nb = 1.710, nc = 1.730.