Geoscience Reference
In-Depth Information
understand the degree of sampling bias within the
sampling scheme. Ideally the petrographer should be
involved in devising the investigation plan and be
present during sampling operations.
The actual sampling technique and the type of sample
required for petrographic examination depend on the
type of material being sampled, the objectives of the
investigation, and if any other types of tests are to be
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Retardation (|sin
|) image of a sandstone sample
obtained using the birefringence microscope imaging
system. This shows the relative birefringence of the
different quartz grains that make up the sandstone;
×150. (Courtesy of Oxford Cryosystems.)
δ
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12
Orientation (
) image of a sandstone sample
obtained using the birefringence microscope imaging
system. The lines show the orientation of the
extinction (slow axis orientation) for each of the quartz
grains; ×150. (Courtesy of Oxford Cryosystems.)
φ
