Chalcedony SiO2

Optical Properties:

Chalcedony is very fine-grained quartz. It commonly occurs as radiating aggregates, as shown in the crossed polarizers view above. First order gray interference color, as in quartz; other optical properties generally are difficult to measure, because of the small grain size.

Occurrence:

Chalcedony occurs as a cement in some clastic sedimentary rocks, as replacement of calcite in come carbonates, and as vesicle fillings in some lavas.

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