Brianite

Brianite is a phosphate mineral with the chemical formula Na₂CaMg(PO₄)₂.[4] It was first identified in an iron meteorite.[3] This mineral is named after Brian Harold Mason (1917–2009), a pioneer in meteoritics.[3]

Brianite
Small white microcrystals of brianite from the Dayton meteorite
General
Category	Phosphate minerals
Formula (repeating unit)	Na2CaMg(PO4)2
IMA symbol	Bne[1]
Strunz classification	8.AC.30
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Unit cell	a = 13.36 Å, b = 5.23 Å, c = 9.13 Å, β = 91.2°; Z = 4
Identification
Color	Colorless
Crystal habit	Anhedral grains with lamellar structur visible under polarized light
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	[2][3][4][5]

It was first reported from the Dayton meteorite in Montgomery County, Ohio in 1966.[3] It occurs in phosphate nodules within the meteorite. Associated minerals include: panethite, whitlockite, albite, enstatite, schreibersite, kamacite, taenite, graphite, sphalerite and troilite.[5]