Nepheline

Nepheline
Nepheline
General
Category	Tectosilicate, feldspathoid
Formula; (repeating unit)	(Na,K)AlSiO4
IMA symbol	Nph
Strunz classification	9.FA.05
Crystal system	Hexagonal
Crystal class	Pyramidal (6) ; H–M symbol: (6)
Space group	P63
Identification
Formula mass	146.08 g/mol
Color	White, gray, brown, brownish gray, or reddish white
Crystal habit	Massive granular to prismatic
Twinning	On [1010], [3365], and [1122]
Cleavage	[1010] Poor
Fracture	Subconchoidal
Mohs scale hardness	6
Luster	Vitreous to greasy
Streak	White
Specific gravity	2.55–2.65 (average: 2.59)
Optical properties	Uniaxial (−)
Refractive index	nω = 1.529–1.546 ; nε = 1.526–1.542
Birefringence	δ = 0.003–0.004
Other characteristics	non-radioactive, non-magnetic, non-fluorescent
References

Nepheline, also called nephelite (from Ancient Greek νεφέλη (nephélē) 'cloud'), is a rock-forming mineral in the feldspathoid group – a silica-undersaturated aluminosilicate, Na₃K Al₄Si₄O₁₆, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites. It is used in glass and ceramic manufacturing and other industries, and has been investigated as an ore of aluminium.

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Nepheline" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 13 August 2022.
^ Nepheline, Mindat.org
^ Barthelmy, David (2014). "Nepheline Mineral Data". Webmineral.com. Retrieved 13 August 2022.