Black crystal aggregates of the very rare Nb-Ta oxide mineral rynersonite in an analyzed specimen from Sweden in a contrasting whitis matrix. From Kårarvet, Falun, Dalarna County, Sweden. Ex. Erich Laskowski collection. — Photo: David Hospital · CC BY-SA 4.0
Rynersonite
A dull fibrous calcium tantalate-niobate of pegmatites.
Intro adapted from Wikipedia (CC BY-SA).
Rynersonite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaTa₂O₆.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Aeschynite structural group.
Key properties: Mohs hardness 4.5; specific gravity 6.402; White streak; Dull, earthy in aggregates luster; optically biaxial.
IMA symbol Rys, IMA status: approved, named in 1974.
A rare alteration product of earlier Nb–Ta minerals in some granite pegmatites.
It is found associated with Fersmite, stibiotantalite, cassiterite, microlite, beyerite, tourmaline, albite, quartz (San Diego Co., California, USA); microlite, wodginite, zircon.
The mineral was named to honor Frederick James Rynerson (1882–1960), and his two sons, Buel Frederick Rynerson (1905–) and Eugene Bonfoey Rynerson (1910–).