mineral
Agate Bookend / Quartz Geode
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale; color ranges from white, translucent, to dyed hues; vitreous to waxy luster; microcrystalline quartz (chalcedony) crystal structure; conchoidal fracture; specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; color ranges from white, translucent, to dyed hues; vitreous to waxy luster; microcrystalline quartz (chalcedony) crystal structure; conchoidal fracture; specific gravity of 2.65.
Formation & geological history
Formed by the deposition of silica from groundwater solutions in the cavities of igneous and sedimentary rocks over millions of years.
Uses & applications
Widely used for decorative home items such as bookends, paperweights, crystal lamps, and in lapidary jewelry.
Geological facts
Agate is a variety of chalcedony that often forms concentric bands inside ancient volcanic vesicles. Many commercial specimens are dyed to enhance their visual appeal.
Field identification & locations
Identified by its distinctive banded patterns, waxy luster, and high hardness that scratches glass. Found worldwide, with major deposits in Brazil, Uruguay, and the USA.
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