| Abstract |
Withamite, a pink-colored epidote, was found several years ago in manganese ore of the Yamanaka mine. Manganese ore mineralization of this mine brought at first the alteration of andesite and rhyolite..., resulting pink withamite in two modes of occurrence as veinlets and disseminated spots. Composite veinlets of withamite with rhodochrosite were found, accompanied by chlorite and fluorite. Zeolitized (analcite) feldspar mass contaminated with withamite were also seen, associated with kaolinite, sericite, montmorillonite, and calcite. Specific gravity of withamite was determined as 3.38 at 18°C by pycnometer. Optic constants were as followings; (-)2V =74°, α= 1.714, β=1.724, γ= 1.730, γ-α=0.016. X=colorless, Y =colorless to pale yellow, and Z= light pink. Chemical formulae was calculated on the basis of O = 13.00. (K_0.01 Na_0.06 Ca_1.80 Mg_0.01 Mn_0.01 Fe"_0.02)1.01 (Fe"'_0.41 Al_2.85)_2.096 (Al_0.15 Si_2.85)_3.00 O_11.70 (OH)_1.30 It shows a good agreement with the ideal formulae of epidote, HR’’_2 R’’’_3 Si_3 O_13. Unit cell dimension was also calculated from the powder data; a_0 = 8.88A, b_0 = 5.61A, co= 10.15A, and β = 115°25'. The mineralogical data are in well correspondence with those of the iron poor pistacite, although the axial colors of this mineral are quite characteristic.show more
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