Black Onyx semiprecious gemstone index and mineral information

At Gemstoneindex you can find information on gemstones, minerals, jewelry, birthstones and more. It is intended as a guide to the beautiful and fascinating world of gemstones.

Throughout history gemstones have been admired and worn as amulets and talismans; believed to have powers to protect against evil, disease, and as safeguards of health. Gemstones have also been worn as a symbol of status of the wearer. In astrology, stones were assigned to each planet, month (birthstones), and even days of the week. Today, some of these associations are still being used, like the connection of gemstones and precious metals with anniversaries, as one example.

Gemstoneindex provides you with historical and scientific facts about gemstones, both precious and semi-precious, including their optical and physical properties, and how and where they are found worldwide. In addition, you will find information on other materials, such as pearl, shell, amber and other descendants of plants or animals. These are called organic gemstones.

Whether you are interested in a gemstone for educational purposes or just to attain knowledge on your favorite stones, you will find a good introduction to the subject here.

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Onyx is the striped semiprecious variety of agate with white and black alternating bands.  The word onyx derives from the Greek word anux or “claw.”  Other varieties of onyx are the carnelian onyx, with white and red bands, and sardonyx, with white and brown bands.

Onyx is made up of black and white bands.  It is similar to agate except that the bands are straight.  Black onyx has almost always been stained.  Natural black onyx is rare and so it is produced by chemically treating agate.  It is also called true onyx or Arabic onyx.  The name onyx properly applies only to the agate variety. It is translucent to nearly opaque with a vitreous luster.

Onyx is also a name sometimes used for unicolored chalcedony. It is popular for carved cameos and intaglios because its layers can be cut to show a color contrast.  Onyx must not be confused with onyx marble, which is a limestone formed by the minerals calcite and aragonite.

Onyx is found in India, Brazil and Uruguay.

Mohs’ hardness: 7