Cornelian or Carnelian is a translucent orange to red variety of chalcedony which is
cryptocrystalline quartz. Its red color is due to the presence of iron impurities in the form
of iron oxide or hematite. It can vary from a flesh red to a clear red. It is usually cut into
cabochons, or into beads, and is also used for intaglios and cameos. Imitations of cornelian
are made by the staining of agate.
Since Cornelian is fairly common, it is an inexpensive gem. The best Cornelian is
translucent. It may be enhanced by being dyed. As noted, Cornelian is often carved and the
quality of carving is a key issue in determining price.
Sources
Originally found in the deserts of Arabia and Egypt, it has also been found in the Rio Grande
area, India, China, Colombia, Saxony, Scotland, West Germany and the United States.
Technical Characteristics
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Chemical Composition:
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SiO2 - Silicon Dioxide
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Hardness:
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7
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Specific Gravity:
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2.65 - 2.66
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Refractive Index (R.I.):
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1.543-1.552 to 1.545-1.554
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Bi-refringence:
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0.009
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Optic Sign:
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Positive
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Optical Character:
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Uniaxial
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Crystal Structure:
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Trigonal
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