Every now and then, a real surprise comes along and makes one step back and wonder about many other things. One such rendering took place this past weekend at the Southwest Gems and Mineral Society Show. Was told by a knowledgable lapidarist when looking at a display I had, than there isn't such a thing as "Black Onyx" which was included in several of the necklace sets I had on display. So started checking around, and the Earth Science Department from Trinity University was present with a booth, so chatted with them for a bit, and yep, no such thing as natural "Black Onyx". To make things easier to understand, here are some definitions of "Black Onyx" off of several different sites on the Internet. .
"Black onyx" is neither truly onyx nor truly black, but it is actually dyed chalcedony. According to some experts, it is produced by boiling slabs of gray chalcedony in a sugar solution. The sugar permeates the stone's "pores" between the submicrocrystallites and darkens the appearance of the stone. This dye/treatment is stable and requires no special care.
"Black onyx" is neither truly onyx nor truly black, but it is actually dyed chalcedony. According to some experts, it is produced by boiling slabs of gray chalcedony in a sugar solution. The sugar permeates the stone's "pores" between the submicrocrystallites and darkens the appearance of the stone. This dye/treatment is stable and requires no special care.
.
Black Onyx - unknown in nature, it is produced by warming chalcedony in a sugar solution for several days or weeks. The stone in then placed in warm sulphuric acid. The acid reacts with the sugar, precipitating the free carbon. The black color is permanent.
.
Black Onyx - Mohs Hardness: 6.5-7 - Treatment: Dyed for color uniformity - Color: clear to browns (See also Chalcedony as no such thing as Black Onyx). Onyx and Sardonyx are similar to agate, but Onyx has straight rather than curved bands. These bands may be in shades of browns, reds, tans, yellow, greens and rarely blues and will always have white. Since ancient Egyptian times, onyx has been stained to improve or change its color to an all black gemstone. All totally black onyx has been produced by soaking black agate (chalcedony)or other Onyx, especially clear, in a sugar solution, then heating it in sulfuric acid to carbonize the sugar particles. Found worldwide. Onyx is formed by the deposition of silica in gas cavities in lava, which results in the distinctive bands.
.
So from now on the proper term to use with the 'little or big black stones' used in jewelry, should be either black Agate or black Chalcedony with the added comment "enhnaced by chemical treatments and is called black Onyx". One learns something new every day if you listen good.
.
.
