Tips and Trips Page 11 The Georgia Mineral Society May 2004 Geology and Selected Minerals of the Diamond Hill Quartz Mine Antreville, South Carolina by Mike Streeter, GMS Member Copyright March 2004 Chrissy and I have spent a great deal of time at the Diamond Diamond Hill is nothing short of remarkable when you consider Hill Quartz Mine near Antreville, South Carolina over the past that the actual collecting areas occupy a total of less than 3 several months. Chester Karwoski, who purchased the acres and that each variety requires its own unique set of property in 2003, brought in some heavy earth-moving conditions to form. The three most sought after varieties of equipment last fall and has opened up some new collecting quartz at the mine are skeletal, smoky and amethyst. opportunities. On our most recent trip to the mine on February 28, 2004, members of the Rome Georgia Gem and Mineral Skeletal quartz (also known Society and the Southern Appalachian Mineral Society joined as elestial quartz) exhibits a us. Since it is no secret that that I am a geologist by trade, I layered or ribbed pattern. am often asked geological and mineralogical questions about Its appearance gave rise to collecting locales. While digging at Diamond Hill, I was asked the term "skeletal" as the to explain how the rocks and crystals formed. Now there's a crystals resemble what $64,000 question for you! I answered the question as best I someone with a good could at the time. Since then, I have researched the literature imagination would expect to obtain a more detailed explanation that I would like to share the skeleton of a quartz with you. crystal to look like (not that they exist). The patterns Diamond Hill has an amazing variety of different quartz crystals exhibited by skeletal quartz including amethyst, smoky, skeletal, milky, clear, and phantom. represent internal and The mine has also become known for the rare phosphate external dissolution-growth features resulting from unstable mineral, cacoxenite conditions during crystallization. At the time that the crystals (pictured on left), first were forming, the conditions were such that the crystals would discovered at the mine alternate between growing and dissolving. This "two-step by chance in late 2002. forward and one-step backward" process resulted in the The quartz crystals are unusual step-like appearance. Very large plates and clusters generally found in clay of skeletal quartz can be recovered from quartz veins in the filled pockets in a eastern end of the upper pit at Diamond Hill. Like much of the series of large quartz other quartz varieties at Diamond Hill, many of the skeletal veins that trend in a quartz crystals exhibit an overgrowth of clear quartz indicating northeast to southwest a later phase of crystallization. This later crystallization forms direction. The quartz "phantoms" where you can see the tips of skeletal quartz veins were emplaced crystals beneath a clear crystal overgrowth that exactly mimics into a granitoid pluton the underlying crystal. (Antreville Pluton) as a result of a series of late Smoky quartz is generally transparent to translucent quartz Paleozoic Era tectonic that is gray to black in color. The characteristic color of smoky events. The Antreville quartz occurs when rock crystal quartz is exposed to natural Pluton, itself, was radiation from radioactive elements or adjacent radioactive intruded during the rocks over long periods of time. The process by which this Taconic orogeny that extended from Late Ordovician to Early occurs is not completely Silurian Periods. Heat and pressure from Paleozoic regional understood but it has been metamorphism transformed the rock into granitoid gneiss. theorized that the color is Silica-rich hydrothermal fluids entered fractures within the the result of altered metamorphosed pluton and deposited the quartz veins. These oxidation states of the veins must have contained voids that would later become sites silica molecules caused by for quartz crystals to form during a series of subsequent radiation. The granitoid hydrothermal events. All of these geological processes took pluton would be the most place miles beneath the present earth's surface. It took over likely natural source of the several hundred million of years of erosion to uncover the radiation. Smoky quartz rocks. The granitoid gneiss has been deeply weathered seems to be most resulting in the development of a thick soil zone made up of concentrated in the lower or western pit at Diamond Hill. Much rock weathered in place. Such in situ weathered rock is called of the smoky quartz appears to have grown in phases saprolite. Oxidation of iron bearing minerals formed clay that represented by larger blocky crystals growing on top of smaller was transported by infiltrating meteoric water into the quartz- crystals. Thin films of silica overgrowths are commonly found lined pockets. Much of the quartz and saprolite is heavily on top of the smoky quartz plates. In some cases, it appears stained with red, brown, yellow and black iron oxides. that the overgrowths have been partially to completely dissolved, indicating an unstable environment during or after The wide variety of quartz crystal varieties that exists at crystallization. Page 12 Tips and Trips May 2004 The Georgia Mineral Society Geology and Selected Minerals of the Diamond The 8th Annual Asheville Gem Fest Hill Quartz Mine Sponsored by the Colburn Museum Antreville, South Carolina The Colburn Gem & Mineral Museum will be sponsoring (continued) the Asheville Gem Fest 2004 on June 18-20, 2004. This will be the 7th year for this annual gem, mineral, and Amethyst is translucent to transparent purple quartz. The jewelry show and sale. The hours of the show will be purple color is thought to be the result of two factors: 1) small Friday, 10:00 A.M. to 8:00 P.M.: Saturday, 10:00 A.M. to amounts of iron impurities at specific sites in the crystal 6:00 P.M.; and Sunday, Noon to 5:00 P.M. Admission to structure and, 2) exposure to natural radiation in a manner the Asheville Gem Fest is free. Admission to the Colburn similar to smoky quartz. Again, the process by which this Earth Science Museum is also free during the show. occurs is not fully understood but it is known that exposing amethyst to sunlight for a long period of time will cause the Gem Fest 2004 will feature over 25 dealers from all purple color to fade. Therefore, it can be concluded that it isn't around the country offering jewelry, mineral specimens, the presence of fossils, gems, beads, lapidary supplies, crystals, books iron alone that and more. causes the purple color or There will be two lectures Saturday afternoon, June 19, else the mineral 2004, by Dr. Michael A. Wise of the Smithsonian. Dr. would not fade Wise’s lectures will be about recent research in simply due to Hiddenite, North Carolina, and the Moorefield Pegmatite sun exposure. Mine in Amelia, Virginia. Amethyst at Diamond Hill The show has something for everyone. Children and generally occurs adults will be able to search for minerals at an outdoor as larger flume, pan for gold, or discover crystal surprises with a secondary geode cracker. The show’s silent auction offers visitors a crystals on top of chance to pick up jewelry, gems, minerals, and gift translucent to certificates and items from local businesses and transparent smaller quartz crystal druzes in quartz vein restaurants at a bargain price. For more information, call pockets in the central portion of the mine. Local rockhounds the Museum at 828.254.7162 or visit our website at use the term "jumping bigger" to refer to this phenomenon and www.colburnmuseum.org. as a key to finding amethyst while digging. My experience has shown that amethyst crystals are almost always found pointed The Colburn Earth Science Museum is located in Pack downward in a pocket and that a hint of purple color can Place Education, Arts & Science Center at 2 South Pack sometimes be found in smoky quartz crystals. Square in downtown Asheville, North Carolina. from a press release from the Colburn Earth Science Museum. If you are looking to find a collecting location that offers a rare opportunity to collect a variety of quartz varieties in one place, Southeast Chapter of Friends of Mineralogy then the Diamond Hill Quartz Mine is your ticket. More Fall Symposium Announcement information about Diamond Hill can be obtained on our website and at www.mcrocks.com. Proceed to the "Field Trips" page to find Call for Abstracts several reports including pictures of the mine and minerals. Additional information, including directions to the mine, can be Plans are already underway for the next Southeast obtained on the Georgia Mineral Society website at Chapter fall symposium on November 13 and 14. We www.gamineral.org/commercial-diamondhill.htm. will once again meet at the Weinman Mineral Museum near Cartersville, Georgia. Talks, auction, and business meeting will take place on Saturday, November 13, and Mike Streeter works as a geologist for the State of North Caro- fieldtrips will take place the following day. This year, we lina and is the author of "A Rockhounding Guide to North Caro- will not have a theme mineral or location, but we lina's Blue Ridge Mountains", April 2003. Check out his web- encourage everyone to consider speaking (for about 15 site at www.mcrocks.com. to 20 minutes) on any mineral related topic that would be of interest to the Southeast Chapter members. Pass It On - Soapstone Please send a title and brief abstract to Julian C. Gray, Chapter president, if you would like to present.