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Onyx is the dark brown to black variety of agate, a cryptocrystalline quartz. Since ancient times onyx has afforded gem cutters and carvers an excellent source for carving cameos, intaglios, and other jewelry creations. Inexpensive, abundant, and available in large sizes, onyx is also a favored stone when fashioning cabochon gems and beads.

Onyx Polished
Onyx Classification
Common Name Onyx
Species Quartz
Onyx Optical Properties
Transparency Semitransparent - Translucent
Dispersion Strength: None
Refractive Index 1.535-1.539
Birefringence 0.004
Optic Character Uniaxial
Optic Sign Positive
Polariscope Reaction Aggregate (AGG)
Fluorescence SWUV: Inert
LWUV: Inert
Pleochroism None
Onyx Characteristic Physical Properties
Hardness 6.5-7
Streak White
Specific Gravity 2.550-2.700 Typical:2.600
Toughness Excellent
Inclusions Onyx will have straight parallel layers of different colors.
Luster Vitreous, Greasy
Stability Good
Fracture Conchoidal, Granular
Cleavage None
Onyx Chemistry & Crystallography
Chemical Name silicon dioxide (aka silica)
Chemical Formula SiO2
Crystal System Trigonal
Chemistry Classification Silicate

Onyx Colors

  • Bi-color Onyx Bi-color
  • Yellow Onyx Yellow
  • White Onyx White
  • Red Onyx Red
  • Purple Onyx Purple
  • Pink Onyx Pink
  • Orange Onyx Orange
  • Multi-color Onyx Multi-color
  • Green Onyx Green
  • Gray Onyx Gray
  • Brown Onyx Brown
  • Blue Onyx Blue
  • Black Onyx Black

Alternate Names

True Onyx, Arabic Onyx

Countries of Origin

United States of America (the); Uruguay; Madagascar; Thailand; India; Canada; Pakistan; China; Ireland; Brazil; Italy; Mexico; South Africa; Peru; Germany; Indonesia


Most black onyx is banded with white in its natural state. It is dyed to emphasize the banding or to eliminate the banding, based on the stone's intended use. Banded stones are ideal for cameos and carvings. Each creates a unique design and is never exactly like another. Onyx is a chalcedony. It's dyed in pleasing blue shades, crisp greens, bright pinks and even white. Primarily known for its deep black color, onyx is a favorite gemstone of jewelry professionals and consumers alike. Paired with summer whites, black onyx adds sophistication to any look.


Much of the onyx sold today is dyed to enhance its color and to afford you years of enjoyment. As with all color-enhanced stones, clean with warm water and mild soap. Rinse thoroughly and dry with a soft cloth. Do not use chemicals, ultrasonic or steam cleaners.

More About Onyx

Somewhere around the mid-1500s, a noted mathematician and astrologer named Girolamo Cardona, wrote that, in India, onyx was used to cool love's ardor. Hmmm… Onyx is listed in the bible as one of the stones on the breastplate of judgement.Other cultures felt that onyx could be used to separate one from an unhappy or unhealthy relationship.Often worn as "mourning jewelry", some people believed that black onyx released sorrow and negative energy.As with all folklore, there is no science that confirms the folkloric attributes of onyx. We can confirm, however, that this shining stone is striking in the right setting and a must-have for any woman's jewelry collection.

Sisk Gemology Reference

Showcasing 200 gemstones in over 1,000 pages and accompanied by more than 2,000 photos, The Sisk Gemology Reference is a must-have in every collector’s library. Each comprehensive, three-volume set features state-of-the-art photography, detailed illustrations, and scientifically precise descriptions to create an entrancing experience for gemstone amateurs and afficionados alike.

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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.