An interferometric examination of synthetic mica (With Plate X)

Abstract

A recent report has appeared describing a process developed in Germany for the production of a crystal described as synthetic mica. The details are given for a process used at Ostheim and reference is also made to a Siemens–Halske technique. Through the courtesy of Mr. Kendall of Metropolitan-Vickers we have secured a few small samples of the Siemens-Halske material. This is reported to be a fluor-phlogopite with the chemical composition KMg₃AlSi₃O₁₀F₂ and free from water of constitution. Claims made by the manufacturers stated that the synthetic material exhibits the cleavage characteristics of natural mica.The few samples we have obtained have areas somewhat less than a square centimetre and we have selected thin cleavage flakes and submitted them to intefferometric examination with the multiple-beam technique.