:A very interesting piece under the microscope. Vesicles in this olivine nephelinite contain microcrystals of orange-brown, prismatic to platy oxykinoshitalite associated with nepheline, calcite, and an apatite group mineral. An unassuming specimen in hand sample, but fairly remarkable under modest magnification. Oxykinoshitalite is a rare and complex barium potassium magnesium titanium iron layer silicate and a member of the Mica Group. Ex. Paulo Matioli collection. 3.0 x 2.0 x 1.0 cm. From: Fernando de Noronha island, Fernando de Noronha archipelago, Pernambuco, Brazil. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Oxykinoshitalite
Oxykinoshitalite is an IMA-recognized mineral species in the silicate class, with the chemical formula BaMg₂Ti⁴⁺O₂(Si₂Al₂)O₁₀.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 2.5; specific gravity 3.3; Brown streak; Vitreous luster; optically biaxial.
IMA symbol Okns, IMA status: approved, named in 2004.
Interstitial in an olivine nephelinite volcanic rock.
It is found associated with Olivine, clinopyroxene, Fe-Ti oxide, nepheline, calcite, apatite, K-rich feldspar.
The oxy-analog of kinoshitalite.