Helvine from the Ilímaussaq intrusion

Abstract

Beryllium minerals are widespread in the Ilimaussaq intrusion. At present, 13 different beryllium minerals have been identified. These are bertrandite, gelbertrandite, spherobertrandite, beryllite, chkalovite, leucophane, epididymite, eudidymite, sorensenite, tugtupite, genthelvite (Semenov, 1969; Engell et a!., 1971), semenovite (Petersen & Rønsbo, 1972) and now helvine. While epididymite occurs as an accessory in the alkali granite (Hamilton, 1964), chkalovite in pegmatites and hydrothermal veins (Engell et al., 1971; Semenov, 1969), all the other recorded beryllium minerals have been found in hydrothermal veins and alteration zones. Engell et al. (1971) reported that leucophane occurs as an accessory in the naujaite referring to the original description of Bøggild (1905). However, this description does not indicate whether the leucophane occurs as an accessory in unaltered naujaite or ifit is related to veins cutting naujaite as recorded by Semenov (1969).