Fluorite is calcium fluoride, CaF, a mineral mined and primarily used for flux in the making of steel. It is a soft mineral (Mohs' hardness of 4) that can be colorless, red, pink, orange, yellow, green, blue, purple, or nearly black. In the United States, major commercial depostits have been mined in the region of the Illinois-Kentucky border. Smaller deposits are widely scattered around the USA.

Pegmatites are intrusive bodies of coarsely crystalline granite-like rock composed mainly of feldspar, quartz and mica. Occasionally, pegmatites contain fine gemmy crystals of tourmaline, topaz and other minerals.. A few unusual pegmatites contain chlorophane, a rare variety of fluorite. Chlorophane is remarkable in that it displays fluorescence, phosphorescence, and thermoluminescence. Some chlorophane will fluoresce blue or green when illuminated with long wave or short wave UV light. When illuminated with a bright visible light source, and then viewed in darkness, chlorophane displays a lingering green to blue glow. This phosphorescent glow can last for many minutes. The most intriguing and distinguishing property of chlorophane fluorite is its thermoluminescence. When heated by flame or electric coil, chlorophane emits a strong bluish light that is observable even in daylight. Although the unique physical properties of chlorophane have been carefully studied by mineralologists and physicists, the reason for the thermoluminescence is not completely understood. It is generally believed that trace amounts of the rare earth elements; terbium, holmium, erbium, and yttrium, are somehow involved.

The classic U.S. locality for cholorphane has been a pegmatite at Amelia Court House, Virginia. Recently, Mitchell and Loretta Warlick of Spruce Pine, North Carolina, have begun mining a small pegmatite located on their property (see above image). The Spruce Pine area is famous for huge pegmatite-like deposits (alaskite) that produce massive amounts of feldspar and quartz, each used repectively in the ceramics and semiconductor industry. Near the huge open pit alaskite mines are much smaller complex pegmatites (e.g. the McHone Mine) that carry mica, aquamarine beryl, morganite beryl, spodumene, tourmaline, topaz, amazonite, lepidolite, petalite, garnet, apatite, chlorophane fluorite and other rare minerals.

The chlorophane from the Warlick's McHone Mine is exceptional for both its strong thermoluminescence, phosphorescence, and unusual color. Fragments of cholorphane from this mine, although only weakly fluorescent, will begin to glow a bluish-green color when heated by the warmth of one's hand (a completely dark room and dark-acclimated eyes are necessary to view this glow). When heated to higher temperature by flame, this chlorophane emits a bright bluish-green glow observable even in daylight! Recently, the Warlicks have recovered small amounts of facet grade chlorphane from their mine. Fragments of this material display good size, excellent clarity, and remarkable thermoluminescence. What makes this cholorphane even more unusual is its color. In daylight the material is a medium, slightly bluish-gray to rose color. When illuminated with tungsten light, the chlorophane is a rose color. Under fluorescent light the chlorophane is a grayish green. McHone Mine chlorophane displays the unusual color-change phenomenon usually associated with the mineral alexandrite. McHone Mine is the new type location for chlorophane fluorite; a very rare and remarkable mineral!

Because fluorite is soft, and cleaves so readily, it is not suitable for jewelry purposes. In spite of this, collectors are drawn to its beautiful colors. Fluorite is not commonly faceted. It is difficult to obtain a brilliant polish on such soft material, and the resulting gems must be treated with great care to avoid damage. Nevertheless, museums and collectors search out and prize faceted fluorites to grace the shelves of their collections. The recent production of color-change, thermoluminescent, chlorophane fluorite has brought a most unusual collector's gem material to the market. Finely faceted chlorophane is as rare and unique as the thermoluminescence it displays.

Mountain Lily Gems has no commercial relationship with the Chalk Mountain Crystal Mine. The following information is provided for rockhounds, mineral collectors, and those interested in visiting a unique U.S. mineral location and gem mine:

The Warlick's Chalk Mountain Crystal Mine (the McHone pegmatite) is open to the public. It is located approximately two miles south of the town of Spruce Pine, N.C., on McHone Road. A flume line for visitors to wash gem gravel, mineral specimens, and a guided tour of the mine are offered. The Warlick's can be contacted by email (Rockwizzard@aol.com) or phone (828-766-8760) to obtain price information and hours of operation.