White masses of nordenskiöldine associated with green masses of danburite. From MW Claim, Screw Creek, Cassiar Mountains, Watson Lake, Yukon, Canada. Ex. Erich Laskowski collection — Photo: David Hospital · CC BY-SA 4.0
Nordenskiöldine
Nordenskiöldine is an IMA-recognized mineral species in the borate class, with the chemical formula CaSn(BO₃)₂.
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Calcite-Dolomite structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 4.09–4.2; Vitreous, pearly on {0001} luster; optically uniaxial.
IMA symbol Nsk, grandfathered status — known before the IMA’s founding, named in 1887.
Very rare in an alkalic pegmatite (Arø Island, Norway); in a hydrothermal deposit in metasomatized marble (Arandis, Namibia); in skarns (China).
It is found associated with Meliphanite, homilite, zircon, molybdenite, cancrinite, analcime, feldspar (Arø Island, Norway); tourmaline, cassiterite, stannite, chalcopyrite, pyrrhotite.
The mineral was named to honor Nils Adolf Erik Nordenskiöld (1832–1901), Swedish mineralogist, geologist, and explorer.