Earth and Planetary Sciences ETDs

Publication Date

Spring 5-26-1951

Abstract

Six anisotropic garnets are studied by optical, thermal, and X-ray diffraction methods in an attempt to determine the cause of anisotropism. The garnets are all ungrandites with compositions ranging from chromian grossularite to nearly pure andradite, the composition having been estimated from indices of refraction and unit cell dimensions. In all cases the birefringence is 0.004 or less. Both positive and negative uniaxial and biaxial figures are sometimes observed. Heating of the garnets at 900°C for periods of 96 to 264 hours reduced the anisotropism in five of the six garnets studied; this observation is in agreement with previously reported studies. Precession and powder X-ray diffraction photographs show no detectable change from unheated to heated samples. Procession photographs of several sectors of a single anisotropic garnet yield identical patterns with isometric Ia3d symmetry, suggesting that anisotropism is not caused by twining. I feel the cause of anisotropism in garnets is due to a combination of strain and rate of crystal growth in the metamorphic environment. A technical garnet bibliography of over 300 papers, written from 1900 to 1960 is presented; papers on anisotropic garnets written before 1900 are also included.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

A. Rosenweig

Second Committee Member

J. Paul Fitzsimmons

Third Committee Member

W.E. Elston

Project Sponsors

Sandia Corporation

Language

English

Keywords

Anisotropism, Garnets

Document Type

Thesis

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