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Layered onyx
MFA# 99.101


A red color Onyx, which is an Agate with parallel bands of Chalcedony. Sardonyx has layers of brownish Sard alternating with lighter-color layers of red Carnelian. Often used as a gemstone, it has been mined or gathered since before 2200 BCE.

Synonyms and Related Terms

onyx; quartz; agate; chalcedony

Sardonyx seal
MFA# 01.7550

Physical and Chemical Properties

  • Fracture = conchoidal, uneven
  • Luster = vitreous to waxy
  • Streak = white
  • Mohs Hardness = 6.5 - 7.0
  • Density = 2.6 g/ml
  • Fluorescence = generally inert
  • Pleochroism = absent
  • Refractive Index = 1.530 - 1.543


Properties of Common Gemstones

Resources and Citations

  • Mineralogy Database: Quartz
  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Wikipedia: Onyx varieties Accessed Dec 2022
  • A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979

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