![]() ![]() Such cavities may form as gas bubbles in a lava flow irregular vugs or open space within a solid rock or horizontal cavities along bedding planes, that result from solution of the preexisting rock, faulting or movement within the rock, or other geologic processes. In general, chalcedony forms by filling cavities in rocks. In the Gila County, chalcedony can assume a wide range of unique and interesting shapes and forms, depending on how, where, and when it formed in the volcanic host rock. (Chalcedony by definition does not show distinct layers of color banding if color banding is present then the specimen is called “agate”.) It has a hardness of 6 to 7 on the Moh’s Scale and a Specific Gravity of 2.6. In terms of color it is most commonly white to gray, sometimes displaying a blue or pink tint due to mineral impurities or an optical phenomena known as Rayleigh Scattering. Chalcedony breaks with a conchoidal fracture and commonly displays a waxy, vitreous, or silky luster. Large Chalcedony vug filling showing botryoidal texture.Ĭhalcedony is best described as a dense, semitransparent or translucent variety of SiO2 consisting of a cryptocrystalline intergrowth of mostly quartz and lesser amounts of moganite, another form of SiO2 that has a different crystal form. Get an E-Mail Notice About New Blog Posts!.
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