Alamosite

Alamosite (Pb₁₂Si₁₂O₃₆) is a colorless silicate mineral named after the place where it was discovered, Álamos, Sonora, Mexico. It is a rare secondary mineral occurring in the oxidized zones of lead-rich deposits. For example, the infobox picture shows its association with black leadhillite.^[2]

Alamosite
Transparent crystals of alamosite in the matrix of leadhillite and melanotekite
General
Category	Inosilicates
Formula	Pb12Si12O36
IMA symbol	Aam[1]
Strunz classification	9.DO.20
Dana classification	65.7.1.1
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2/c
Unit cell	a = 11.209, b = 7.041 c = 12.22 [Å]; β = 113.15°; Z = 12
Identification
Color	Colorless
Cleavage	{010} perfect
Mohs scale hardness	4.5
Luster	Adamantine
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	6.49
Optical properties	Biaxial (−)
Refractive index	nα = 1.947, nβ = 1.961, nγ = 1.968
Birefringence	δ = 0.021
2V angle	65° (meas.)
References	[2][3]