Geodes are more or less spherical nodules of chalcedony with an interior that may be hollow or (partially) filled with quartz. Quartz and chalcedony are, respectively, the crystalline and amorphous (non-crystalline) variety of silica (SiO2).The chalcedony in geodes may also be referred to as agate, but that term is meant to indicate a chalcedony of semi-precious quality, discussed in the next chapter. Flintstone, chert and silex are other denominations for chalcedony.
KeywordsVolcanic Rock Quartz Crystal Golf Ball Actual Diameter Rhyolitic Lava
Unable to display preview. Download preview PDF.