White sharp crystals of the very rare lead mineral nasonite from the famous locality of Langban (Värmland, Sweden) in a matrix of manganophyllite. — Photo: David Hospital · CC BY-SA 4.0
Nasonite
Nasonite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₄Pb₆(Si₂O₇)₃Cl₂.
It crystallizes in the hexagonal crystal system (space group P6_3/m).
Key properties: Mohs hardness 4; specific gravity 5.42–5.55; typically white or colorless; white streak; Greasy to adamantine luster; optically uniaxial.
IMA symbol Nso, grandfathered status — known before the IMA’s founding, named in 1899.
A rare mineral, formed under hydrothermal conditions, cutting franklinite- willemite ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA); in calcite-filled veins in a metamorphosed Fe{Mn deposit (Lºangban, Sweden).
It is found associated with Clinohedrite, barysilite, datolite, prehnite, willemite, axinite, hancockite, garnet, manganophyllite (Franklin, New Jersey, USA); manganoan diopside.
The name refers to Frank Lewis Nason (1856–1928), American geologist, Geological Survey of New Jersey, USA.
Collections: Collector Favorites, Rare & Remarkable.