search
  • Sign In
    Sign Up
  • English speaking customer support only

    Toll Free - USA & Canada only:
    1-800-464-1640

    International:
    +66-39303404

  • Change Language
  • USD

Onyx Stone - Gemstones

Antique Onyx Cameo

Most people think of onyx as a black gemstone, but this is actually misleading in two ways. In the gemological world, the term onyx refers to layered stones that exhibit different colors in multiple layers. Usually this material is cut from agate or other types of chalcedony with even, parallel layers, usually with a lighter layer above a darker one.

Onyx may be a multilayered black and white stone, usually with a black base and a white upper layer. But it may also be brown and white, as in sardonyx; or red and white as in cornelian onyx. These types of onyx were traditionally used in gem carving and engraving, where the multiple layers in the stone could be used to produce interesting effects. Well known types of engravings include intaglio, where a negative image is created; and cameo, which is a raised relief.

What then is the black gemstone commonly known today as onyx? Usually it is agate or chalcedony which has been dyed to make it a uniform black color. It is usually cut as cabochons or beads, though more recently it has been faceted as well.

Sardonyx Rough Stone

The name onyx has sometimes been used - quite incorrectly - to refer to other banded lapidary materials, such as calcite found in Mexico and Pakistan. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as 'onyx' today are actually this carbonate material.

Natural onyx is similar to other cryptocrystalline quartz, with a hardness of 6.5 to 7 on the Mohs scale. Like all quartz, it is silicon dioxide with a density of 2.58-2.65 and a refractive index of 1.530-1.540.

Since black gemstones can make elegant jewelry, black onyx has become very popular. There are actually relatively few gemstones that occur in black. Onyx is the most common and least expensive of all black gemstones. Other gem varieties that occur in black include diamond, sapphire, spinel, jet and tourmaline. In the finer gems, black tourmaline is the most widely available and still sells at very affordable prices.

  • First Published: February-13-2009
  • Last Updated: January-23-2019
  • © 2005-2019 GemSelect.com all rights reserved.
    Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.
Pinterest Board Names
More Shapes
Popular Gemstones
  • Sapphire
  • Emerald
  • Ruby
  • Aquamarine
  • Zircon
  • Opal
  • Topaz
  • Tourmaline
  • Garnet
  • Amethyst
  • Citrine
  • Tanzanite
All Gemstones (145)
A B C D E F G H I J K L M N O P Q R S T V Z
  • Actinolite Cat's Eye
  • Agate
  • Agate Geode
  • Almandine Garnet
  • Amazonite
  • Amethyst
  • Ametrine
  • Ammolite
  • Andalusite
  • Andesine Labradorite
  • Apatite
  • Aquamarine
  • Aventurine
  • Beryl
  • Black Opal
  • Bloodstone
  • Boulder Opal
  • Calcite
  • Carnelian
  • Cat's Eye Apatite
  • Cat's Eye Aquamarine
  • Cat's Eye Augite
  • Cat's Eye Gemstones
  • Cat's Eye Moonstone
  • Cat's Eye Opal
  • Cat's Eye Scapolite
  • Chalcedony
  • Charoite
  • Chocolate Opal
  • Chrome Diopside
  • Chrome Tourmaline
  • Chrysoberyl
  • Chrysocolla
  • Chrysoprase
  • Citrine
  • Color-Change Diaspore
  • Color-Change Fluorite
  • Color-Change Garnet
  • Color-Change Sapphire
  • Coral
  • Demantoid Garnet
  • Dendritic Agate
  • Diamond
  • Druzy Amethyst
  • Druzy Azurite
  • Druzy Citrine
  • Emerald
  • Enstatite
  • Fire Agate
  • Fire Opal
  • Fluorite
  • Fossil Coral
  • Garnet
  • Golden Beryl
  • Grandidierite
  • Grossularite Garnet
  • Hawk's Eye
  • Hematite
  • Hemimorphite Druzy
  • Hessonite Garnet
  • Hiddenite
  • Howlite
  • Idocrase
  • Imperial Topaz
  • Iolite
  • Jade Gemstones
  • Jadeite
  • Jasper
  • Kornerupine
  • Kunzite
  • Kyanite
  • Labradorite
  • Lapis Lazuli
  • Larimar
  • Malachite
  • Malaya Garnet
  • Mali Garnet
  • Maw-Sit-Sit
  • Moonstone
  • Morganite
  • Moss Opal
  • Mother of Pearl
  • Mystic Quartz
  • Mystic Topaz
  • Nuummite
  • Obsidian
  • Opal
  • Opal Doublet
  • Opal in Matrix
  • Pearl
  • Peridot
  • Pietersite
  • Prehnite
  • Pyrite
  • Pyrope Garnet
  • Quartz
  • Quartz Cat's Eye
  • Quartz With Marcasite
  • Rainbow Moonstone
  • Rainbow Pyrite
  • Rhodochrosite
  • Rhodolite Garnet
  • Rhodonite
  • Rose Quartz
  • Rubellite Tourmaline
  • Ruby
  • Ruby in Fuchsite
  • Ruby-Zoisite
  • Rutile Quartz
  • Sapphire
  • Scolecite
  • Seraphinite
  • Serpentine
  • Sillimanite
  • Sillimanite Cat's Eye
  • Smithsonite
  • Smoky Quartz
  • Snowflake Obsidian
  • Sodalite
  • Spectrolite
  • Spessartite Garnet
  • Sphalerite
  • Sphene
  • Spinel
  • Star Diopside
  • Star Garnet
  • Star Gemstones
  • Star Lemon Quartz
  • Star Moonstone
  • Star Rose Quartz
  • Star Ruby
  • Star Sapphire
  • Star Sunstone
  • Strawberry Quartz
  • Sugilite
  • Sunstone
  • Tanzanite
  • Tiger's Eye
  • Tiger's Eye Matrix
  • Topaz
  • Tourmaline
  • Tsavorite Garnet
  • Turquoise
  • Variscite
  • Zircon
Main Categories
  • New Arrivals
  • Gemstone Lots
  • Calibrated Gemstones
  • Gemstones By Piece
  • Top Grade Gems
  • Matching Pairs
  • Cabochon Gemstones
  • Drilled Gems, Briolettes and Beads
  • Birthstones
  • Gemstone Carvings
  • Fancy Gemstones
  • Star Gemstones
  • Unheated Sapphire
English speaking customer support only

Toll Free - USA & Canada only:
1-800-464-1640

International:
+66-39303404

Save Money
No shipping Fees for Additional Items!
$8.90 Worldwide Shipping

Update Translation
 
Current Value
New Value
GemSelect Gemstones
X Close Window
Colored Gemstones
X Close Window
Colored Gemstones
X Close Window
Colored Gemstones
Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart