Park County yields treasure trove of chalcedony and petrified wood
Luke Sattler (USA)
I recently took a field trip to the Hartsel and South Park area of Colorado with my brother, grandparents, Steven Veatch (the Pikes Peak Pebble Pups Leader) and his wife, Shelly. We went to look at two pieces of real property owned by Steven Veatchin South Park, which together consisted of a large expanse of flat grazing land, bounded by mountains.
Within seconds of arriving,my grandmother found some beautiful blue chalcedony and some large, very smooth, jet black nodules that may also be chalcedony. Other colours of chalcedony were found, as well as petrified wood. Everyone spread out quickly to find jasper of several colours, together with flaked jasper formed by American Indians (who were fashioning arrowheads centuries ago), magnetite and unakite.
Chalcedony is a cryptocrystalline form of silica; its chemical composition is SiO2 (silicon dioxide). It forms in low temperature solutions, unlike crystalline quartz, which forms atmuch higher temperatures (Ralph and Chau, 1993-2012). Chalcedony’s lustre is dull to waxy,while the hardness of chalcedony is 6 to 7, and it has a fracture of uneven to conchoidal. The usual colour of chalcedony is white, but there are many forms of chalcedony that include carnelian, chrysoprase (green chalcedony), heliotrope (bloodstone), onyx,agate and moss agate.
The specimens of chalcedony that my grandmother found – some with agate banding – are from a site near Hartsel in the South Park Ranches Subdivision. The material here occurs in veins and, over time, weathersfree, whichallows for easy collecting. This sort of material is called “float” (Fig. 1).
Chalcedony at this site has also formed into a crystalline habit known as botryoidal, whichmeans‘grape-like’ in Greek. This grape formation occurs when thick mineral fluids form around a particle into a jelly-like substance inside a void and solidifies – leaving a bubbly surfaceon the outside (Smigle, 2012). And some of the collected material had small vugs or cavities in which small drusy quartz crystals grew to form small, very attractive geodes (Fig.2).
Exploring the property not only gave rise toa great afternoon and fantastic views,but also provided us with a great collecting opportunity,during which we found – in only a few hours – various kinds of chalcedony and even some beautiful examples of petrified wood.
About the author
When Luke wrote this article, he was an avid rock, mineral and fossil collector. He was a member of the Colorado Springs Mineralogical Society and participates in the youth division. At that time, Luke had written a number of papers on the geosciences and had been published throughout the USA.
References
Ralph, J., & Chau, I. (1993-2012). Chalcedony. Retrieved from http://www.mindat.org/min-960.html.