Onyx is a fine–grained type of the mineral compound chalcedony, which is being prized as a gem quality stone. The stone is also made up of compositions of submicroscopic crystals or aphanitic  types of the quartz. It has an interchanging parallel and regular layer of unusual and different shades of colors which particularly includes the color white, brown, and black. Cameo brooches are most of the time being carved from this stone with the layer of white color which stood up in aid against of a dark-shaded background.
The stone is composed of the mineral compound silicon dioxide. It has a hardness of 7 in Mohs scale and a specific gravity of not less than 2.5 and not exceeding more than 2.8. The gemstone also has a positive optic sign and a uniaxial optical character.
Such specimens are widely used for cameos, as stated, which are carved to give a raised design in a particular in contrary to a background of another, in which is especially a pale head against a darker background. Onyx was very much known to ancient Romans in their time, which used this for vases, cups, and objects of the similar varieties.
Sardonyx is a fine variant of onyx, which eventually contains colored bands known as sard, which are shades of red, rather than black. The most common among all types of onyx is the pure black, and conceivably perhaps the most famous of its variety, but extremely not as much common as the gemstone with bands of colors.
The gem quality stone is commonly being cut into beads, or as a cabochon, and is also very much widely used for intaglios. It is in these placements where the bands of colors make the image in contrary with the ground. Occasionally, some onyx is much produced by staining of agate, but the natural ones are the best varieties.
The onyx is the birthstone for those who were born under the Western zodiac sign, Leo, and the Oriental sign of the zodiac, Ox. It can be many different numbers of colors, but astrologically speaking, the ones of the reddish brown shades are the more preferred varieties. It is believed that Onyx exiles one’s grief away and brings fortune to those who brings the stone and serves as its possessor, which brings more confidence of personal strengths and enhances revival, visceral, sensitivity, and perception. It was also believed to help change, delete, and disregard bad habits.
Onyx has sometimes been manipulated wrongly to seal some other banded engraved gemstone and of the same materials, such are namely banded calcite which are found widely in Mexico, Pakistan, Northern India, and in other similar places, and are every so often carved, polished at some extent, and are then being sold in the market. The said compound mineral is much softer than the true Onyx and more eagerly available. Most of the items being carved that are sold as “onyx” at these times are those under the carbonate matters.
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