Farneseite
A cancrinite-group silicate with an unusual 14-layer stacking sequence, named for Farnese in Lazio, Italy.
Intro adapted from Wikipedia (CC BY-SA).
Farneseite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₄₆Ca₁₀(Si₄₂Al₄₂O₁₆₈)(SO₄)₁₂·6H₂O.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Cancrinite-sodalite structural group.
Key properties: Mohs hardness 5; specific gravity 2.425; White streak; Vitreous luster; refractive index 1.501; optically uniaxial.
IMA symbol Far, IMA status: approved, named in 2004.
Found in vugs between interlocking sanidine within a syenitic pyroclastic rock.
It is found associated with Sanidine, andradite, clinopyroxene (augite), biotite, Fe-oxides, feldspathoids.
The name is derived from the locality, Farnese, that produced the first specimens.