Hodgkinsonite: Gemstone Information
Pink transparent hodgkinsonite, Mn2Zn2SiO4(OH)2 occurs as stout prismatic crystals of the monoclinic system with steep pyramids or with dominating pyramids. There is one direction of perfect cleavage; the hardness is 5 and the SG 4.06–4.08. The RI for the alpha, beta and gamma rays is 1.720–1.724, 1.741–1.742, 1.746, biaxial negative with birefringence 0.026. Pleochroic colours are lavender and pale purple. Specimens may show a dull red fluorescence under LWUV. Hodgkinsonite occurs as seams in massive willemite-franklinite granular ore in a metamorphosed stratiform zinc deposit. The only significant occurrence is at Franklin,New Jersey, USA.