A survey of feldspar twinning

Forelesninger holdt ved Advanced Study Institute of Feldspar - Oslo 1962
Lectures held at Advanced Study Institute of Feldspar - Oslo 1962

A common feature of the feldspars, triclinic as well as monoclinie, is the frequent occurrence of twinning, more than twenty different laws having been described. As is well known to petrologists, the twinning of plagioclases plays an important role in the determination of the anorthite content by microscopic methods. But besides this practical aspect, the twinning of the feldspars also offers interesting problems from a purely crystallographical point of view. It is therefore believed that a general survey of the hitherto described twinning laws may well be presented in this place.