Scorzalite

Scorzalite
Scorzalite from the Estaño Orcko mine, Potosí Department, Bolivia (6.8 x 5.7 x 5.1 cm)
General
Category	Phosphate minerals
Formula (repeating unit)	(Fe2+,Mg)Al2(OH,PO4)2
Strunz classification	8.BB.40
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2/c
Unit cell	a = 7.15 Å, b = 7.31 Å c = 7.25 Å; β = 120.58°; Z = 2
Identification
Color	Dark blue
Crystal habit	Granular, massive, dipyramidal crystals
Twinning	Multiple, lamellar
Cleavage	Good on {110}, indistinct on {101}
Fracture	Uneven
Mohs scale hardness	6
Luster	Vitreous
Streak	White
Diaphaneity	Semitransparent
Specific gravity	3.33
Optical properties	Biaxial (-)
Refractive index	nα = 1.626 - 1.645 nβ = 1.654 - 1.674 nγ = 1.663 - 1.680
Birefringence	δ = 0.037
Pleochroism	Visible X = colorless; Y = Z = blue
2V angle	Measured: 62°
Dispersion	r < v perceptible
References

Scorzalite ((Fe²⁺,Mg)Al₂(OH,PO₄)₂) is a dark blue phosphate mineral containing iron, magnesium, and aluminium phosphate. Scorzalite forms one endmember of a solid solution series with the lighter, more magnesium-rich lazulite.

Scorzalite crystallizes in the monoclinic system in a dipyramidal form. It has a Mohs hardness of 5.5-6 and a specific gravity of 3.4. It is infusible and insoluble in water, and only slightly soluble in warm hydrochloric acid.

It was first described in 1947 for an occurrence in the granite pegmatite in the Córrego Frio mine, Linópolis, Doce valley, Minas Gerais, Brazil. It was named for the Brazilian geologist Everisto Pena Scorza (1899–1969).

It occurs as a secondary phase in pegmatites and kyanite (aluminium-rich) quartzites. Associated minerals include souzalite, triphylite, wyllieite, trolleite, apatite, lacroixite, berlinite, tourmaline, muscovite, feldspar and quartz.