Open AccessTwins in cryolite types from Ivigtut, South Greenland
Author(s) -
Hons Pauly
Publication year - 1978
Publication title -
bulletin of the geological society of denmark
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.674
H-Index - 28
eISSN - 2245-7070
pISSN - 0011-6297
DOI - 10.37570/bgsd-1978-si-02
Subject(s) - cryolite , fluorite , sample (material) , geology , geochemistry , metallurgy , chemistry , materials science , aluminium , chromatography
The appearance of twins in various coarse grained tYPes of cryolite from Ivigtut is illustrated. The examination is based on large thin sections (from 5 cm to 12 cm across) of pure, white large-grained cryolite, similar large-grained cryolite from fluorspar-cryolite and from a vein of pure, black cryolite in the wallrocks. The seven twin laws identified by B0ggild (1911, 1912) were found in most samples. The sample from fluorite· cryolite was dominated by the twin law (001) and the sample from the vein was dominated by [021)120• The general picture seems to favour a mechanical formation of all twins in the samples. The characteristic parting of cryolite is intimately related to the presence of twin lamellae, mainly as reported by B0ggild (1911, 1912), corresponding to the law [021]"0 but also (110) (B0ggild 1913), and (001) as observed in the sample from fluorite-cryolite here examined. This sample also contains indications for several stages of reorientation presumably in response to outside stress situations.