Phyllite Thin Section in Polarized Light

An examination of geological thin sections of the mineral phyllite using polarizing microscopy, as well as providing information on component minerals, can reveal a great deal about how the rock was formed.

Phyllite (above) illuminated with plane-polarized light.

Phyllite (above) as imaged through crossed
polarized illumination.

Phyllite (above) imaged with crossed polarizers and a
full-wave (first order) retardation plate inserted
between the specimen and analyzer.

Phyllite, a metamorphic rock, clearly shows the alignment of crystals under the effects of heat and stress. Small scale folds are visible in the plane-polarized image and more clearly defined under crossed polars with and without the wave plate. The crossed polars image reveals that there are several minerals present--quartz in grey and whites and micas in higher order colors. The alignment of the micas is clearly apparent. Addition of the wave plate improves contrast for clear definition in the image.

Thin sections of the mineral were polished and sealed with a cover glass, then observed and photographed using a Nikon Eclipse E600 microscope equipped with crossed polarizers and an intermediate tube containing an insertable retardation plate. The scale bar represents 500 microns.


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Contributing Authors

Phillip C. Robinson - Department of Ceramic Technology, Staffordshire Polytechnic, College Road, Stroke-on-Trent, ST4 2DE United Kingdom.

Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.