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Wonderful summary by Susan Acosta (CCR&MC Recording Secretary) The program tonight was presented by Adam and Teresa Dean. He is known as the "Agate Hunter". He is Co-chair of the Southern California part of CFMS for field trips. The topic he chose was "Pseudomorphs and Epimorphs of the Cady Mountains"Zeolites are a group of minerals that form into agates and sagenite (the fans in agate structures). Epi refers to the minerals that forms on the surface of another mineral. It is an epimorph after, if the original mineral has been dissolved or weathered away. It would be an epimorph on if the original mineral is still there. Eolites are composed of hydrated aluminosilicate. there are many types. Both pseudomorphs and epimorphs are created from zeolites plus other minerals. There are open lattice structures or tubes and pockets - as exemplified by mesolite, stilbite natrolite, etc. The Cady Mountain agates are related to zeolite combinations of barite and calcite. Epimorphs can be almost anything and can appear like coating over the original structure. It is more resistant to acids. Crystal growths occur on the surface of another mineral. He showed slides of various minerals to explain what he had spoken of: Chalcedony after an unknown zeolite; angel wing agate which has a mineral deposit with surface tension in basalt plume agate, which are usually red with arborescence (tree like structures); fortification agate which was white/grey plus some color; sagenite. He suggested that rock and mineral clubs should file claims before all public land is closed to rock hunting. At the end of his talk he showed slides of the areas where he and his wife found the various specimens shown. He also showed some slabs, rough and polished, from the various mines they own. It was most informative and interesting. |
