Onyx 
Mohs scale hardness: 7
Onyx is a semi-precious gemstone made of silicon dioxide and belongs to the chalcedony family of colored quartz. The stones are classified as chalcedony if they are milky, and transparent to translucent, often with bands or layers of colour. The colours of its bands range from white to almost any colour but the most common contain bands of colours of white, brown and tan. Black onyx is highly valuable and other colours can also be found. Onyx is very commonly dyed to give it darker or “blacker”. Since the stone is porous (like any other chalcedony), it absorbs color quite easily.
Onyx Jewelry
In a piece of onyx jewelry, sometimes most of the value comes from its design and not in the gemstone material. The quality of the surface will determine the value of the stone, the polish should be shiny and reflective throughout the stone’s surface in an evenly manner. There should not be any pits or cracks, you can observe the surface of the gem with a loupe (gemological magnifying glass). The gem should be slightly transparent.
The most well known type of onyx is black onyx and is also the type which is most often found in jewelry. Black onyx is the aniversary gemstone for the 10th year of marriage. Onyx is normally shaped into cabochon or beads. The type of onyx in which the bands are in shade of red instead of black is called sardonyx. The colour of onyx is often the result of chemical and heat treatment, even many of the dealers do not know wether the gems are natural or not because it is difficult to distinguish. Many onyx gemstones are natural in form but most of it is also produced when one stains the agate.
Cameos are cut from stones, such as onyx, agate or sardonyx, where different colors occur in layers. They cut away the background material, leaving the cameo design in relief. The stone is also used in intaglios, its layers can be cut to show a color contrast betwen the design and the background. Onyx may scratch or chip easily so extra care should be taken when handling it. It can be cleaned using a mild soap and lukewarm water. Rinse the gem properly with water and then dried in open air.
It is believed onyx has special properties:
• A healing stone for ailments of the kidneys and heart.
• Black onyx can change wearer’s bad habits.
• Can make the wearer become eloquent.
• To reduce neurological disorders, stress and maintain a good night’s sleep.
• Capable of pacifying the over-eagerness on love.
• To help in the growth of skin, fingernail and hairs.
• Able to get rid of negative thoughts, sharpening the wits and giving spiritual inspiration.
Astrologically, onyx is associated with the zodiac signs of Leo and it is the mystical birthstone for the month of December. Onyx is also the anniversary gemstone for 7th year of marriage.
Sardonyx Healing Properties
Sardonyx is a reddish-brown onyx.
Sardonyx is the most valuable gemstone of the chalcedony family. The name of the gem was probably acquired because of the fusionn of certain qualities of sard with onyx. Sardonyx is also the traditional birthstone for august. In ancient times, Egyptians used these gemstones as talismans and many Roman soldiers wore sardonyx gems engraved with heroes and the god of war such as Mars or Hercules Ares to render them fearless and brave in battles. According to gem lore, orange sardonyx stimulates, black sardonyx absorbs negative energies and green sardonyx can purify. Sardonyx is also used or worn by public speakers and leaders to bring them luck and making the listeners agree or support them.
Sardonyx at one time was more precious than sapphire, silver or even gold. Perhaps the most famous sardonyx was the one set in the ring of gold and carved with the portrait of Elizabeth I and the Queen gave it to the Earl of Essex (Queen’s lover) as keepsake and memento. Just like many other gemstones, sardonyx also needs to be avoided from extended exposure to extremes of heat or chemicals which could damage the gems. The stone is always widely used in intaglios and cameos. Sardonyx can be found in Germany, Brazil, Czechoslovakia, Mexico, United States, Russia, India and Africa.
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