Experiments on the simultaneous exchange of Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, Mn²⁺, Ca²⁺ and Sr²⁺ between hedenbergite or tremolite and 2M aqueous chloride solutions were carried out in the temperature range of 500 to 800°C, 1 kb. The PC-IR curves for the both minerals show a similar shape and have peaks near Ni²⁺ and Ca²⁺. The former peak corresponds to 6 coordination and the latter peak to 8 coordination. The PC-IR curves suggest that Ni²⁺, Mg²⁺ and Fe²⁺ are partitioned preferably in 6 coordination of the minerals and Mn²⁺, Ca²⁺ and Sr²⁺ in 8 coordination. However Co²⁺ and Zn²⁺ deviate from such a trend. The ion selectivity decreases with increasing temperature.

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Chemical evolution of ferrocolumbites from the Ishikawa-yama granitic pegmatites, Fukushima, Japan, has been revealed by electron microprobe analysis. The compositions of ferrocolumbites are different among sample locations, which are within about 1 km distant from each other. Three discernible trends in compositional variations in ferrocolumbites have been observed: (1) a homogeneous crystal trend, with low Ta/(Ta + Nb); (2) a trend with oscillatory zoning related to Ta and Nb; (3) a trend with patchy zoning related to Fe and Mn. Oscillatory zoning of ferrocolumbite is intimately related to crystal growth in magmatic process. Ferrocolumbite with patchy zoning shows parallel extinction and doesn’t appear to have the complementary distribution of octahedral cations due to some coupled substitutions on the plots of partition coefficient (each zone/the assumed average) against ionic radius. These facts and the curved boundaries of patchy zoning suggest that patchy zoning of ferrocolumbite has been produced by topotaxy in the open system.

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Some euhedral crystals of borate minerals were found in vugs and fissures in veins intruded into crystalline limestone near the gehlenite-spurrite skarns at the Fuka mine, Okayama Prefecture, Japan. The interfacial angle of the euhedral crystals was measured using a one circle reflecting goniometer. Used euhedral crystals are frolovite, henmilite, hexahydroborite, nifontovite, olshanskyite, pentahydroborite and uralborite. The possible indices of plane and zone axis were calculated from the unit cell parameters of each mineral, and compared with the average values of measurements. The indices of plane and zone axis were determined with maximum error of ±1.5 degree between the average value of measurements and calculated value. The crystal forms of frolovite, hexahydroborite, nifontovite, olshanskyite and uralborite are the first report in the world. The crystal forms of henmilite and pentahydroborite reported previously were corrected.

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