Electronic Resource
Springer
Contributions to mineralogy and petrology
25 (1970), S. 66-76
ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Coal macerals are often, as is well known, optically anisotropic. Recent charcoal, carboniferous fusinite and carboniferous vitrinite were measured: 1. with a special goniometer, 2. in a microscope with vertical illumination between crossed polarizers, 3. with a mica compensator. The measurements with the special goniometer and photomultiplier gave characteristic curves. The minimum of these curves is the Brewster angle, which is constant for a particular material. The value of the Brewster angle is different parallel and perpendicular to the direction of the seam respectively. While the sample is rotating (360°) in a microscope between the crossed polarizers the value of reflectivity changes in a characteristically symmetrical manner. There is good agreement with the goniometer measurement. To study the influence of absorption similar curves were produced for quartz, turmaline and vitrain. It was possible to find the retardation in a layer of vitrain by means of a very sensitive elliptical compensator. The absolute value of this retardation is extremely small, its mathematical sign coincides with the results of the other experiments.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00383063
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