Lazulite

Lazulite
Lazulite
	Lazulite specimen found near Rapid Creek, Yukon, Canada
General
Category	Phosphate mineral
Formula; (repeating unit)	(Mg,Fe2+)Al2(PO4)2(OH)2
IMA symbol	Lzl
Strunz classification	8.BB.40
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) ; (same H–M symbol)
Space group	P21/c
Unit cell	a = 7.144(1), b = 7.278(1) ; c = 7.228(1) [Å]; β = 120.5(1)°; Z = 2
Identification
Color	Azure, sky blue, bluish white, yellow-green, blue-green, rarely green
Crystal habit	Tabular, acute to stubby bipyramidal crystals; granular, massive
Twinning	Common by several twin laws
Cleavage	Poor to good on {110}, indistinct on {101}
Fracture	Uneven, splintery
Tenacity	Brittle
Mohs scale hardness	5.5–6.0
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent to nearly opaque
Specific gravity	3.122–3.240
Optical properties	Biaxial (−)
Refractive index	nα = 1.604–1.626; nβ = 1.626–1.654; nγ = 1.637–1.663
Birefringence	δ = 0.033–0.037
Pleochroism	Strong: X = colorless, Y = blue, Z = darker blue
2V angle	Measured: 61–70°
Fusibility	Infusible
Solubility	Insoluble
References

Lazulite is a transparent to semi-opaque, blue mineral that is a phosphate of magnesium, iron, and aluminium, with the chemical formula (Mg,Fe²⁺)Al₂(PO₄)₂(OH)₂.^[3] Lazulite forms one endmember of a solid solution series with the darker, iron-rich scorzalite.^[3]^[5]

Lazulite crystallizes in the monoclinic system. Its crystal habits include steep bipyramidal or wedge-shaped crystals.^[6] Lazulite has a Mohs hardness of 5.5–6.0 and a specific gravity of 3.0–3.1. It is infusible and insoluble.^[5]

^ Warr, L. N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3). Mineralogical Society of Great Britain and Ireland: 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Cite error: The named reference HBM was invoked but never defined (see the help page).
^ ^a ^b ^c Lazulite, Mindat.org
^ Lazulite Mineral Data, WebMineral.com
^ ^a ^b ^c Hurlbut, Cornelius S.; Klein, Cornelius (1985). Manual of Mineralogy (20th ed.). Wiley. ISBN 0-471-80580-7.
^ "Lazulite". Minerals.net.