Nosean

nosean

sanidine

zircon

leucite

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Formula: Na₈(Si₆Al₆)O₂₄(SO₄).H₂O
Tectosilicate (framework silicate), sodalite group, forms discontinuous solid solution with haüyne
Crystal System: Isometric
Specific gravity: 2.3 to 2.4 measured, 2.21 calculated
Hardness: 5½
Streak: Bluish white
Colour: Colourless, white, grey, grey-brown, blue, black
Solubility: Gelatinises in acids
Environments

Volcanic igneous environments

Nosean typically occurs in alkali-rich silica-deficient volcanic rocks, particularly phonolite, and in volcanic bombs (Dana). Associated minerals include sanidine, mica, leucite, magnetite, ilmenite, titanite and zircon (HOM, Mindat).

Localities

At the Canary and Cape Verde Islands, nosean occurs in phonolite (Dana).

At the type locality, Sandkuhle, Maria Laach, Glees, Brohltal, Ahrweiler District, Rhineland-Palatinate, Germany, nosean is associated with zircon, sanidine, mica and magnetite (Mindat).

In the Cripple Creek Mining District, Teller Co., Colorado, USA, nosean is a common constituent of rocks including phonolite, plagioclase phonolite and tephritic-phonolite. Nosean is one of the first minerals to form, in pale blue to green crystals to 2 mm (Minrec 36.2.175).

In Lawrence county, South Dakota, USA, nosean occurs in phonolite and tinguaite (Dana).

In the La Sal Mining District, North Mountain, La Sal Mountains, Grand county, Utah, USA, nosean occurs in phonolite and tinguaite (Dana).

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