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.


Volcanic Rock Quartz Crystal Golf Ball Actual Diameter Rhyolitic Lava 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Dirk J. Wiersam

There are no affiliations available

Personalised recommendations