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By Reviewed By Andreas Zabczyk Mar 07, 2014 Updated Jan 17, 2019

Onyx Gemstone Information

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About Onyx - History and Introduction

Onyx is black and white banded agate (cryptocrystalline or chalcedony quartz). It should not to be confused with onyx marble, which is limestone. The banding of onyx is parallel and consistent. Some varieties of onyx differ in color, such as sard onyx, which has a brown base and white upper layer, cornelian onyx, which has a red base and white upper layer, and niccolo onyx, which has a very thin upper layer, allowing the black base color to show through as grey or blue. Onyx takes its name from the Greek word "onux", which means fingernail; this could be due to a Greek legend, in which Eros mischievously cut the fingernails of Aphrodite with an arrowhead whilst she slept, and the gods turned the clippings into stone. Onyx was cut and carved as a gemstone by the Ancient Greeks and Romans in cameos. Intaglio etchings (negative relief engravings) were also made from onyx. These carvings showcase the banding of onyx.

Onyx Gemstone

Identifying Onyx

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Onyx can be identified by its black base and white upper layer with parallel banding. However, in the case of sard onyx the base is brown and cornelian onyx has a red base. It is difficult to identify when the material is a single color and can only be clearly distinguished from agate when seen in the rough, exhibiting visibly parallel and consistent banding.

Onyx; Origin and Gemstone Sources

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Onyx deposits are found in countries all over the world, including Argentina, Australia, Brazil, India, Botswana, Madagascar, Mexico, Myanmar (Burma), Pakistan, Sri Lanka, Uruguay and the USA.

Buying Onyx and Determining Onyx Gemstone Value

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Onyx Color

Onyx has a black base and white upper layer, but may contain bands of various other colors between these layers. In gemstones, onyx may also be one single color. In the case of sard onyx, the base layer is brown, cornelian onyx has a red base layer and niccolo onyx has a very thin upper layer, which allows the black base layer to show through as grey or blue. A lot of onyx gemstones are completely black.

Onyx Clarity and Luster

Onyx has a waxy to dull luster and is typically opaque. Gemstones are typically free from inclusions.

Onyx Cut and Shape

Due to its bands of color, onyx is often carved into beautiful cameos which maximize the banding. It is also cut into glossy cabochons or faceted. Onyx can also be drilled to make beads or pendants.

Onyx Treatment

Onyx is usually dyed to enhance its color and produce a uniform hue. Such methods have been used for hundreds of years. A black color is achieved with the use of concentrated honey or sugar solution after heated sulphuric acid treatment. All reputable gemstone suppliers declare any treatment or enhancement.

Onyx Gemological Properties:

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Chemical Formula: SiO2 Silicon dioxide
Crystal Structure: Trigonal, microcrystalline aggregates
Color: Black based with white upper layer; various colors
Hardness: 6.5 - 7 on the Mohs scale
Refractive Index: 1.530 - 1.540
Density: 2.58 - 2.64
Cleavage: None
Transparency: Opaque
Double Refraction or Birefringence: Up to 0.004
Luster: Waxy to dull
Fluorescence: Varies according to bands: Partly strong; yellow, blue-white

Please refer to our Gemstone Glossary for details of gemology-related terms.

Onyx: Related or Similar Gemstones

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Multicolor Agade Geode
Multicolor Agate Geode

Since onyx is silicon dioxide, it is related to all of the other types of quartz, especially cryptocrystalline quartz types such as agate, chrysoprase, jasper, carnelian and bloodstone. Onyx can appear similar to schorl tourmaline, black jade, black diamond and jet.

Onyx Gemstone Mythology, Metaphysical and Healing Powers

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Black onyx is thought to have protective properties and to bring inner strength, self-confidence and mental discipline to its wearer. Additionally, onyx is said to help to release negative emotions and alleviate fear and anxiety. Physically, onyx is believed to help in wound healing, childbirth, eye and ear problems and to benefit the skin, hair, teeth and nails. Onyx is the birthstone for the zodiacal sign of Leo and the seventh wedding anniversary gemstone. Like many gemstones, some cultures believe onyx to be unlucky, but others consider it to be virtuous and to protect against black magic.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Traditional, Ceremonial and Mythological Gemstone Lore is collected from various resources and does not represent the sole opinion of SETT Co., Ltd. This information is not to replace the advice of your doctor. Should you have any medical conditions, please see a licensed medical practitioner. GemSelect does not guarantee any claims or statements of healing or astrological birthstone powers and cannot be held liable under any circumstances.

Onyx Gemstone and Jewelry Design Ideas

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Onyx is a versatile material that can be fashioned into a wide variety of jewelry that displays its unique banding or a single color. Black onyx is commonly used for both men's and women's jewelry. Onyx contrasts well with gold settings that give it a bold appearance. In Victorian times, onyx was popular as mourning jewelry and black onyx provided a dramatic contrast in silver set Art Deco jewelry. Onyx is beautiful by itself and stunning alongside diamonds and other colored gemstones, such as in the Van Cleef & Arpels "Manhattan Flowers"; earrings made from moonstone, onyx and diamond that were worn by Adele at the 2012 Brit Awards.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamonds by weight in comparison.

Famous Onyx Gemstones

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The largest surviving ancient cameo is The Great Cameo of France, dating back to approximately 23 AD. The cameo is carved from five-layer sard onyx and features twenty-four figures on three levels. It is currently displayed in the Bibliotheque Nationale, in France.

The Gemma Augustea (Gem of Augustus) is another remarkable cameo, carved from Arabian onyx. It is thought that Dioscurides (A Roman physician, pharmacologist and botanist) or one of his associates created the cameo in the 1st century AD. The Gemma Augusta features twelve figures and is an exhibit of the Kunsthistorisches Museum in Vienna.

The Fabergé Trans-Siberian Railway Egg, created in 1900 for Tsar Nicholas II of Russia is made of onyx, silver, gold and quartz. It is currently on display in the Kremlin Armoury Museum in Moscow, Russia.

Onyx Gemstone Jewelry Care and Cleaning

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How to clean your gemstonesOnyx is a fairly tough substance but still requires proper care to keep it in good condition. To clean your onyx, simply use soapy water and a soft cloth. Be sure to rinse well to remove soapy residue. As with most gemstones, ultrasonic cleaners and steamers are not recommended. Always remove any jewelry or gemstones before exercising, cleaning or engaging in harsh physical activities such as sports. Onyx can be easily scratched by harder substances, so it should be stored away from other gemstones. It is best to wrap gemstones in soft cloth or place them inside a fabric-lined jewelry box.

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