Faujasite

Faujasite
General
Category	Zeolite
Formula (repeating unit)	(Na2,Ca,Mg)3.5[Al7Si17O48]·32(H2O)[1]
IMA symbol	Fau[2]
Strunz classification	9.GD.30
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H–M Symbol (4/m 3 2/m)
Space group	Fd3m
Unit cell	a = 24.638–24.65 Å, Z = 32
Identification
Color	Colorless, white
Crystal habit	Octahedral or rarely trisoctahedral crystals up to 4 mm in size
Twinning	on {111}, contact and penetration twins
Cleavage	{111}, perfect
Fracture	Uneven to conchoidal
Tenacity	Brittle
Mohs scale hardness	4.5-5
Luster	Vitreous to adamantine
Streak	White
Diaphaneity	Transparent
Specific gravity	1.92–1.93
Optical properties	Isotropic
Refractive index	n = 1.466–1.480
Pleochroism	None
References	[3][4][5]

Faujasite (FAU-type zeolite) is a mineral group in the zeolite family of silicate minerals. The group consists of faujasite-Na, faujasite-Mg and faujasite-Ca. They all share the same basic formula (Na₂,Ca,Mg)_3.5[Al₇Si₁₇O₄₈]·32(H₂O) by varying the amounts of sodium, magnesium and calcium.^[1] Faujasite occurs as a rare mineral in several locations worldwide.

Faujasite materials are widely synthesized industrially. The relatively low-silica (Si/Al<2) synthetic faujasite is called Zeolite X and the high-silica (Si/Al>2) one is called Zeolite Y. In addition, the aluminum component in zeolite Y can be removed by acid-treatment and/or steam-treatment, and the resulting faujasite is called USY (Ultrastable zeolite Y). USY is used in fluid catalytic cracking process as a catalyst.