Abstract
Johannsenite from the Koryu mine, a gold-silver vein deposit of epithermal type, occurs as a principal constituent of gold-silver quartz veins. It is found as crustified bands in the form of aggregates of very fine crystals, less than 1 μm in length, and sometimes as acicular or fibrous crystals about 10 μm or less in length. Its unitcell parameters are a = 9.875(4), b = 9.044(4), c = 5.274(2)Å, and β = 105.54(9)°. Its chemical composition ranges from 57.7 to 75.6 mole% CaMnSi2O6, 14.0 to 23.9 mole% CaMgSi2O6, and 10.4 to 18.4 mole% CaFeSi2O6.
