Bromargyrite

Bromargyrite
Bromargyrite with Silver - San Onofre, Mexico.
General
Category	Halide minerals
Formula (repeating unit)	AgBr
Strunz classification	3.AA.15
Crystal system	Isometric
Crystal class	Hexoctahedral (m3m) H-M symbol (4/m 3 2/m)
Space group	Fm3m
Unit cell	a = 5.7745 Å; Z = 4
Identification
Color	Yellowish, greenish brown, bright green
Cleavage	None observed
Fracture	Irregular/uneven, sub-conchoidal
Tenacity	Sectile
Mohs scale hardness	2½
Luster	Adamantine, resinous, waxy
Streak	White to yellowish white
Diaphaneity	Transparent, translucent
Specific gravity	6.474
Optical properties	Isotropic
Refractive index	n = 2.253
Birefringence	δ = 0.000
References

Bromyrite or bromargyrite is a natural mineral form of silver bromide found mainly in Mexico and Chile. Hardness is 1.5 to 2. Related are chlorargyrite and iodyrite.

It was first described in 1859 for an occurrence in Plateros, Zacatecas, Mexico where it occurred in a silver deposit as an oxidation product of primary ore minerals. It occurs in arid environments along with native silver, iodargyrite and smithsonite along with iron and manganese oxide minerals.