Triplite and wolframite from a greisen-bordered veinlet in Eurajoki, SW Finland

Abstract

Triplite and wolframite are described from a greisen-bordered veinlet associated with the local varieties of the Laitila rapakivi granite massif. The chemical analysis, unit cell dimensions and specific gravity are given for these minerals, and in addition the optical properties and the indexed powder diffraction data for triplite. Single-crystal studies of triplite gave a space group I2, I2/m or Im, and a pseudo space group I2/c or 1c. A comparison is made with other mineral occurrences of the same type. The hybnerite-ferberite ratio (0.29) of the wolframite is within the range generally observed for wolframites occurring in greisen veins and quartz veins.