Well-formed crystals are rarely found—a true geological mystery. Most of these rare rose quartz crystals are from Minas Gerais, Brazil. Rose quartz is generally found in massive chucks associated with pegmatites (figure 1). The term pegmatite refers to the texture of certain coarse-grained crystalline granites. Since rose quartz is cloudy, it is not popular as a faceted gem but is commonly cut into cabochons (figure 2), rounded into beads for necklaces, or carved.
|Figure 1. This large rose quartz specimen was found at the Devil's Hole Mine, about a mile from the town of Cotopaxi, Colorado. Photo date 2007, © by A. Schaak.|
Figure 2. A cabochon pendant from the same rose quartz boulder in figure 1. Photo date 2007,© by A. Schaak.
Blue quartz gets it deep to sky blue color from inclusions that scatter sunlight from inclusions. These inclusions could be tiny mineral grains of: ilmenite, rutile, tourmaline, crocidolite, magnesioriebeckite, or zoisite (maybe others). Inclusions selectively scatter visible light of the shorter, blue wavelength. Blue quartz has opalescence (waxy luster), chatoyancy (alternating luster), and asterism (presence of star-like figures).
|Figure 3. These blue quartz megacrystals are located in the pegmatites of the Cape Ann Granite at Andrew’s Point in Rockport, Massachusetts. Photo date 2007, © by H. Renyck.|
|Figure 4. Close up view of blue quartz in Cape Ann Granite at Andrew’s Point in Rockport, Massachusetts. Photo date 2007, © by H. Renyck.|
Coblieg, T., 1986. Why is Blue Quartz Blue?, Geological Society of America 18: 567.
Frondel, C., 1962. The System of Mineralogy, 7th edition, vol. 3, Silica Minerals, John Wiley and Sons Publishers, N.Y., 334 p.
Koivula, j., 2003,. Blue Quartz. Gems & Gemology 39, p. 44-45.
Romero Silva, J.C. 1996. Blue Quartz from the Atequera-Olvera Ophite, Malaga, Spain. The Mineralogical Record 27, p. 99-103.
Rossman, G. R., 1994. Colored Varieties of the Silica Minerals: in Silica: Physical Behavior, Geochemistry and Materials Applications, edited by P.J. Heaney, C.T. Prewitt, and G. V. Gibbs, Washington, D.C., Mineralogical Society of America, Reviews in Mineralogy, vol. 29, p. 433-468.
Wise, M. A., 1981. Blue Quartz in Virginia, Virginia Minerals 27, p. 9-13.
Zolensky, M. E., Sylvester, P.J., and Paces, J. B., 1988. Origin and significance of blue coloration in quartz from Llano rhyolite (Illanite), north-central Llano County, Texas. American Mineralogist, 73, p. 313-232.