Rock crystal

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Description

Colorless, transparent quartz. Rock crystal has been gathered or mined since Paleolithic times. Sources include India, Egypt, Hungary, Spain, Cyprus near Paphos, Kharga oasis, the Alps, and Turkey near Lake Van. Rock crystals were used in rings, bracelets, seals, cups, and carvings. In Egypt, they were also used for the cornea portion of stone eyes in statues and as thin inlays over red cement to simulate carnelian (Aston et al 2000). Currently rock crystals are used in optical instruments as lens and prisms; in circuitry as piezoelectrical devices; and as a semiprecious gemstone.

Quartz crystal

Synonyms and Related Terms

rhinestone; quartz crystal; Herkimer diamonds; Pecos diamonds; cristal de roca (Esp.); cristal de roche (Fr;); cristal de roche (Port.); bergkristal (Ned.)

Other Properties

Usually occurs as six-sided prism. Trigonal crystal system. Low birefringence.

Low thermal expansion.

Fracture = conchoidal. Luster = vitreous to greasy. Streak = white.

Composition SiO2
Mohs Hardness 7.0
Density 2.65

Additional Information

° B.Aston, J.Harrell, I.Shaw, "Stone" in Ancient Egyptian Materials and Technology, P.Nicholson, I.Shaw (eds.), Cambridge University Press, 2000, p. 52. ° Mineralogy Database: Quartz

Comparisons

Natural and Simulated Diamonds

Properties of Common Gemstones


Sources Checked for Data in Record

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 644
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
  • A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962
  • Encyclopedia Britannica, http://www.britannica.com Comment: "rock crystal." Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service 7 Apr. 2005 .
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Tom Rowland, Noel Riley, A-Z Guide to Cleaning, Conserving and Repairing Antiques, Constable and Co., Ltd., London, 1981

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