|VUG IN SANDSTONE COLLECTED AT COPPER RIVET MINE. NOTE GEMMY CLEAR CALCITE PARTIALLY ENCRUSTED WITH GREEN MALACHITE AND BLUE AZURITE. NOTE TINY GREEN ACICULAR CRYSTALS NEAR LOWER LEFT PART OF SPECIMEN.|
At the Tucson Electric Park/Kino Complex show I purchased an interesting specimen collected from the Copper Rivet Mine (uranium and copper) in Mesa County, Colorado, about 10 miles south of Gateway (Juanita Arch Quadrangle, 38.535ºN, 108.975ºW). The seller indicated the specimens were collected in the early 1960's and that he had purchased a flat for resale; I immediately snapped up one!
Thus far I have not had access to an appropriate geological library to locate geological information. However, the mine is very near the Utah-Colorado state line in an area of copper production; MinDat (www.mindat.org) noted that the Copper Rivet is located several miles north of the Cashin Mine. The North Jeffco Gem and Mineral Club collected at the mine in a 2000 field trip that is described at peaktopeak.com/njeffco/2000/copperrivet/copper00_rep.php. They described the hike to the dump and mine adit as 'strenuous".
The specimen, ~2.5 x 2.5 inches, has gemmy clear calcite crystals with coatings of boytrodal malachite and microcrystals of azurite appearing as "blobs". And, there are quite tiny, green acicular crystals of what I am guessing is malachite although their green color is a different shade than the boytrodal form. MinDat listed the following minerals known from the Copper Rivet: Azurite, Baryte, Bornite, Calcite, Chalcocite, Chalcopyrite, Luzonite, Malachite.
|PHOTOMICROGRAPH OF SPECIMEN SHOWING BOYTRODAL MALACHITE (~2 MM), BLUE AZURITE, CLEAR CALCITE.|
|PHOTOMICROGRAPH OF SPECIMEN EMPHASIZING GREEN ACICULAR CRYSTALS.|