Iodargyrite

Iodyrite or iodargyrite is a natural mineral form of silver iodide.

Iodargyrite
Iodargyrite on gossan, Broken Hill Ore Deposit, New South Wales, Australia.
General
Category	Halide minerals
Formula	AgI
IMA symbol	Iag[1]
Strunz classification	3.AA.10
Crystal system	Hexagonal
Crystal class	Dihexagonal pyramidal (6mm) H-M symbol: (6mm)
Space group	P6mm
Unit cell	a = 4.59, c = 7.51 [Å]; Z = 2
Identification
Color	Colorless (fresh); pale yellow, yellow, greenish yellow, brownish, grayish
Mohs scale hardness	1+1⁄2 – 2
Luster	Adamantine, resinous
Streak	Yellow (shining)
Diaphaneity	Transparent, translucent
Specific gravity	5.69
Optical properties	Uniaxial (+)
Refractive index	nω = 2.210 nε = 2.220
Birefringence	δ = 0.010
References	[2][3]

Related minerals are chlorargyrite and bromargyrite.