Sursassite

Sursassite is a sorosilicate mineral. It was first discovered in 1926.^[4] It was first found in the Sursass (Oberhalbstein), a district of Graubünden, Switzerland. It is generally found in deposits of metamorphosed manganese.^[5]

Sursassite
General
Category	Sorosilicate
Formula	Mn2+2Al3(SiO4)(Si2O7)(OH)3
IMA symbol	Ss[1]
Strunz classification	9.BG.15
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/m
Identification
Color	Red-brown to copper-red
Crystal habit	Botryoidal
Cleavage	[101] Distinct
Mohs scale hardness	3
Luster	Silky, Dull
Streak	yellow-brown
Diaphaneity	Translucent
Density	3.256
Optical properties	Biaxial
Refractive index	1.73 to 1.76
Birefringence	0.030
Pleochroism	Strong; X = Z = colorless to pale yellow; Y = deep golden brown.
Dispersion	r > v
References	[2][3]