Remember the crab fire agate beads I bought a while ago? I was trying to find out what they were and guessed that they were actually carnelian? Well pin a gold star on me because it turns out I was right.
I just got the newest newsletter from the Gemological Institute of America and 'fire agate' is described this way:
A new type of treated chalcedony now flooding the market is being misrepresented as "fire agate." Fire agate is a brown chalcedony that displays iridescence, commanding a higher price than most chalcedonies. This new material, however, resembles carnelian or sard marked by a network of white lines.
The GIA Laboratory acquired several strands of beads fashioned from this material at the Tucson gem show and cut some in half to examine the nature of the white lines. All the beads were identified as chalcedony on the basis of their gemological properties. When the cut halves were examined with magnification, they showed fractures that for the most part penetrated to a similar depth from the polished surface, and the white lines followed these fractures exactly. Because the fractures were directly related to the surface of the beads, they must have been induced artificially (such as by quench crackling). The white lines were undoubtedly the result of some form of bleaching process that penetrated into the fractures.
It is readily apparent that this chalcedony is treated and is very different from fire agate. Dyed colors such as green and purple are also being seen.
The strands I bought are much prettier than the ones pictured here though. Mine are a bright golden orange, not a brown. Deelish!
