The dye used in the process is stable and one should be careful while cleaning to avoid removing or dulling this stone. The natural onyx is extremely rare to be found. Most of the black onyx which is produced commercially is heated and permanently dyed to enhance the depth of the black color making it exotic. This method is in use since ages and said to produce permanent result. If these stones are further put into Sulfuric acid the sugar will carbonize producing black color onyx. The porous bands will absorb the liquid and when heated the sugar will caramelize producing deep brown color. In fact one can make black onyx by keeping banded agate into the solution of honey and sugar water over low heat for couple of days. Black onyx was first made some 4000 years back in Harappan civilization. Dyeing is a process to alter the color of a gem by dipping it in a solution to allow the dye penetrates through fractures present in the stone. Right from the antiquity Onyx as a stone is dyed to improve the color and texture. The specific gravity ranges from 2.65 to 2.66.The Refractive index or R.I is 1.543-1.552 to 1.545- 1.554.The optical sign is positive with uni axial optical character.
A type of microcrystalline Silicon dioxide it is used extensively for carving and no doubt in great demand with lapidary artists due to its hardness which is 7 on Mohs scale.
This stone is mined in many countries including Brazil, Mexico, England, Pakistan, Uruguay, India and California. Sardonyx is onyx with white bands or ribbons on black or brown background and is different from black colored onyx.īlack onyx is most commonly available stone world over. Used traditionally for carving cameos, you will often find it as shiny background for any jewelry due to its fine texture and smoothness. It is basically Agate which is dyed to get the black color. Coming in varieties of colors including brown, white, grey and black the one which looks most stunning is the black Onyx. The attributes ranges from translucent to opaque in some stones and strongly white or black banded. It is known as ‘nail of a finger or claw’ in Greek mythology. Onyx is one of the banded varieties of Chalcedony or Agate. An anniversary gemstone for the 10th year of marriage black onyx looks elegant as a piece of jewelry.
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