Very pale green inclusions of the very rare borate numanoite, in sharp crystals of the also rare borate borcarite with which it forms a partial series, from the the type locality for numanoite: Fuka Mine, Bitchu-cho, Takahashi, Honshu Island, Japan. — Photo: David Hospital · CC BY-SA 4.0
Numanoite
Numanoite is an IMA-recognized mineral species in the borate class, with the chemical formula Ca₄CuB₄O₆(OH)₆(CO₃)₂.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 4.5; specific gravity 2.96; White to pale blue-green streak; Vitreous luster; optically biaxial.
IMA symbol Num, IMA status: approved, named in 2005.
On the wall of cavities in a vein of nifontovite or in fractures in a crystalline limestone near gehlenite-spurrite skarns. Likely formed by Cu- and Mg-bearing late hydrothermal solutions.
It is found associated with Borcarite, nifontovite, bultfonteinite, calcite.
The mineral was named to honor Tadayuki Numano (1931-2001), Emeritus Professor, Okayama University, Japan.