Buergerite

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Buergerite
Category	Mineral
Chemical formula	NaFe³⁺₃A_l6(BO₃)₃Si₆O₂₁F
Identification
Molecular Weight	1,052.34 gm
Color	Bronze, Dark brown, Black
Crystal system	Trigonal - Ditrigonal Pyramidal
Cleavage	Distinct/Good on {1120}
Mohs Scale hardness	7
Optical Properties	Uniaxial (-)
Birefringence	δ = 0.080
Streak	yellowish brown
Density	3.31
Diaphaneity	Translucent to Opaque

Buergerite is a mineral species belonging to the tourmaline group. It was approved as a mineral in 1966 by the IMA and named in honor of Martin J. Buerger (1903-1986), a Professor of Mineralogy at the Massacusetts Institute of Technology and a pioneer of crystal structure analysis. There are only three know locations world wide that Buergerite has been found at: Mexico the type locality, Brazil, and the Czech Republic.