The Onyx Problem
Why should onyx be a problem? It is because there are four different stones called onyx by different people.
The name "onyx" comes from the Greek meaning "fingernail." It describes stones that, like nails, are somewhat translucent and strongly banded. Some two millennia ago Pliny the Elder (who died in the Vesuvius eruption of 79 A.D.) wrote of two different stones called onyx. One was suitable as a building material. The other was a gemstone.
The building stone is a form of calcite called travertine. Just to confuse things, it is often called Egyptian alabaster, alabaster and marble onyx. (Many thanks to Dr. Urbano Nuviala of Zaragosa, Spain for this information and references.) Alabaster is compacted, fine-grain gypsum. The two rocks resemble each other, but Egyptian alabaster and Mexican tecali are really travertine. I made this common mistake when I first posted this page. Even the Third International Dictionary defines tecali as alabaster (see below).
Travertine has a long history. The Egyptians used it for some of their carvings, for example for canopic jars, into which the vital organs of the dead were placed. The history of the use of this stone in Mexico is also quite long (see Tecali: The Other Precious Stone). Today, the material is cut into paperweights, little boxes, beads and other things for the tourist trade in Mexico and Egypt. Pakistan and Argentina have similar deposits; we are investigating them.
Pliny's gemstone onyx is a humanly altered agate. Banded agate can be turned into onyx by soaking it in a solution of honey or sugar water over a low heat for a couple of weeks. The duller, slightly porous bands will soak up some of this liquid, and when the stone is heated, the sugar will caramelize in them and turn brown. The less porous white bands remain unaffected, emphasizing the contrast. The result is a brown onyx, deeply and attractively banded.
If the sugar-impregnated stone is put into sulfuric acid, the sugar will carbonize and become black. An even handsomer black onyx will result. The Harappans were making brown onyx some 4000 years ago. Arikamedu (q.v.) is the place where the first black onyx is thus far recorded, more than 2000 years ago.
The fact that nearly all gem onyx requires induced color surprises many people. There is natural onyx, but it is very rare. The only piece in the Center's collection is from a suburb of Pune, India. I found it in the garden of a house I lived in; it is a microlith blade core.
The fourth onyx, the one many people today think of when they hear this word, is completely black chalcedony. Chalcedony (the agate family) worked at Idar-Oberstein, Germany comes from Minas Gerais ("General Mines") state in Brazil. It is often quite uniform or with little banding. The Germans treat it as described above for black onyx and the result is an all black stone, but technically not onyx, as it has no banding. True black chalcedony is "Lydian stone," used for touchstones. An experienced jeweler can tell within a karat the fineness of gold with a touchstone. In the Bronze Age, touchstones were used for testing bronze objects in the same way.
P.S. Webster's Third International Dictionary. It defines "onyx" first as a banded agate, then as black onyx and then as alabaster. As an adjective, it describes anything that is "jet black," using another stone to describe the color.
Incidentally, "tecali" is also in the Third International. I wasn't looking it up. It happens to be the far-left index word on page 2348 in the third volume. (Thanks guys for putting out the much more manageable three-volume set a well as the one volume monster.) It incorrectly defines tecali as alabaster. The also have the etymology wrong. They say [Sp tecali, fr. Tecali, village in Puebla, Mexico]. It should read [Sp fr. Nahuatl fr. te- stone + calle house].
When is someone going to donate any edition of the OED? We would have so much fun with it.
: James A. Harrell 1990 Misuse of the Term "Alabaster" in Egyptology. Gottinger Miszellen 119:37-42.
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