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 Main Menu > GeoGallery > Minerals > Quartz > Quartz 
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Quartz Quartz crystal/agate cylinder. There are two main groups of quartz: chert and chalcedony. Chalcedony is composed of fibrous crystals intergrown, yielding a variety of patterns including agate. Agate is a variety of chalcedony composed of concentric bands of colors. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.
Group: Oxides |
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