Brianite

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Brianite
General
Category Phosphate minerals
Formula
(repeating unit)
Na2CaMg(PO4)2
Strunz classification 08.AC.30
Crystal symmetry Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 21/a
Unit cell a = 13.36 Å, b = 5.23 Å, c = 9.13 Å, β = 91.2°
Identification
Color Colorless
Crystal habit Anhedral grains with lamellar structur visible under polarized light
Crystal system Monoclinic
Twinning Polysynthetic on {100}
Mohs scale hardness 4-5
Luster Vitreous
Diaphaneity Transparent
Specific gravity 3.0-3.1
Optical properties biaxial (-)
Refractive index nα = 1.598, nβ = 1.605, nγ = 1.608
Birefringence 0.010
2V angle 63° to 65°
Extinction 2 to 3° from lamellae
References [1][2][3]

Brianite is a phosphate mineral with the chemical formula Na2CaMg(PO4)2.[2] It was first identified in an iron meteorite.[1] This mineral is named after Brian Harold Mason (1917-2009), a pioneer in meteoritics.[1]

It was first reported from the Dayton meteorite in Montgomery County, Ohio in 1966.[1] It occurs in phosphate nodules within the meteorite. Associated minerals include: panethite, whitlockite, albite, enstatite, schreibersite, kamacite, taenite, graphite, sphalerite and troilite.[3]

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