Manjiroite , Todorokite , Calcite Locality: Wessels Mine (Wessel's Mine), Hotazel, Kalahari manganese fields, Northern Cape Province , South Africa ( Locality at mindat.org ) Size: 9.2 x 8.8 x 6.7 cm. Manjiroite and todorokite are RARE to uncommon hydrated manganese oxides. This exceptionally rich and showy specimen consists of bedded, dark gray, lamellar manjiroite altering to todorokite with really neat-looking vugs lined with glassy calcite crystals. Some of the lamellar manganese oxides are chatoyant! A nifty and unusual specimen from the Willy Israel Collection, who purchased this excellent piece from well-known dealer Clive Queit in 1986. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Manjiroite
Manjiroite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Na(Mn⁴⁺₇Mn³⁺)O₁₆.
It crystallizes in the tetragonal crystal system. It is a member of the Coronadite structural group.
Key properties: specific gravity 4.29; Brownish black streak; Dull luster.
IMA symbol Mji, IMA status: approved, named in 1966.
Found in the oxidation zone of metamorphosed bedded manganese deposits.
It is found associated with Pyrolusite, nsutite, birnessite, cryptomelane, goethite (Kohare mine, Japan); cryptomelane, pyrolusite, nsutite, roman`echite (Pilbara, Australia).
The mineral was named to honor Dr. Manjiro Watanabe (1891-?), Emeritus Professor of Mineralogy, Tohoku University, Sendai, Japan.