Abstract

The name sarcopside, originally given by Websky to a mineral mixture from Michelsdorf, Silesia was shown by Čech, Padĕra and Povondra to be an intergrowth of graftonite and another mineral which has now assumed the name sarcopside. In a restudy of this material and similar intergrowths from East Alstead and Deering, New Hampshire, a third mineral, vivianite, was found to be present. It appears certain that earlier chemical analyses were made on mixtures of graftonite, sarcopside and vivianite

Data for sarcopside from East Alstead, New Hampshire follows. Electron probe analysis gives: FeO 50.2, MnO 6.9, MgO 3.5, P2O5 39.8, total 100.4. Formula: (Fe, Mn, Mg)8(PO4)2. X-ray study yields: a = 10.47 Å, b = 4.80, c = 6.06, β~90°, P21/a. a:b:c = 2.181:1:1.263. Specific gravity 3.79 (meas.), 3.798 (cal. for two formula-units per unit cell). Optically biaxial (—); α = 1.670, β = 1.728, γ = 1.732, 2V = 28°. Optical orientation appears to be consistant with triclinic not monoclinic symmetry. Polysynthetically twinned on [001].

The oriented lamellar intergrowth is viewed as the result of the breakdown of an original homogeneous phase, (Fe, Mn, Ca, Mg)3(PO4)2, into two phases, sarcopside and graftonite. The present study established that all the CaO and a relatively high proportion of the MnO are concentrated in the graftonite.

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