![]() RUSK COUNTY: Corundum is sparsely found as tiny grains in the Barron quartzite in the Blue Hills east of Rice Lake (Ernst et al., 1980). ![]() OUTAGAMIE COUNTY: Rare ruby and an occasional sapphire are reported from stream gravels throughout the county, particularly in the gravel pits near Oneida (Eckert, 1980) and Seymour (Crowns, 1976). Even these few reports must be viewed with caution, as red garnet is easily mistaken for ruby and blue zircon mistaken for sapphire.īARRON COUNTY: Trace amounts of corundum have been found as tiny grains in the Barron quartzite in the Blue Hills east of Rice Lake (Ernst, et al., 1980).īROWN COUNTY: Eckert (1980) reports corundum as both sapphire and ruby found on rare occasions in the gravel pits of the Green Bay area.ĬHIPPEWA COUNTY: Corundum is sparsely found as tiny grains in the Barron quartzite in the Blue Hills east of Rice Lake (Ernst et al., 1980).ĭODGE COUNTY: Hawley and Beavan (1934) reports a small number of clastic corundum grains within the Mayville iron ore. If blue, the uses of sapphire are a good guideline. As a variety of corundum, sapphires come in all colors. Different varieties of corundum are distinguished by characteristics of color, transparency, internal features, and optical phenomena. Rough blue sapphire crystal in cornflower blue. If red, consider designing as if it were ruby. Old lawn chairs may be coated with a thin layer of corundum if their aluminum surfaces have oxidized. Corundum is extremely rare in Wisconsin, being found exclusively as a redeposited sedimentary mineral. Designing with Corundum With its hardness and durability, corundum can be used in jewelry designs that see high traffic or likelihood of impacts: bracelets, rings, anklets, etc. Corundum survives erosion and weathering, and can be found as a heavy mineral in sands and gravels. It can be found in silica-under saturated igneous rocks such as syenite or in certain schist with unusually high amounts of alumina and low amounts of silica. ![]() More often, it is found as drabber blue to blue-gray crystals. (Photo by Andrew Silver.)ĭescription: Corundum is most famous for its rare colored varieties: the bright red ruby and the deep blue sapphire. Geological Survey Denver Library Photographic Collection. From the mineral collection of Brigham Young University Department of Geology, Provo, Utah, Mineral Specimens 419.
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