I'm no expert, but to me that looks like some sort of resin being exposed by a chip.
The ones I see in china are not resin but stone (agate) that is acid (or whatever chemical process) etched and distressed. The MORE distressed looking ones are sold for lower prices than the shiny, smooth ones, as if they are seconds. I, for one, LIKE the distressed look.
The designation "etched" for this class of beads is a misnomer, from the early days of archaeology. The first beads that were recovered (such as at Ur) were thought to be "etched" because those particular specimens had lost the white part of the decoration, leaving a recessed pattern in the ground of the stone (which was carnelian). They were therafter called "etched carnelians"--and the name has stuck.
Then, perhaps as recently as the 20th C., certain carnelian ornaments actually were acid-etched, creating a decoration that similarly had a recessed appearance. So, the confusion continued.
A better name for the process is "chemical decoration." I routinely call these "decorated stone beads." The way the process works, a liquid compound is made from sal soda, combined with water and viscous plant juice (and sometimes lead powder--though there are most likely several variations, since we are talking about processes that go back to 2,500 BCE). The compound is "painted" onto the bead using a pointed implement, and is allowed to dry. The stone is then fired. The application is fused into the stone, and becomes a permanent part--even submerging into the stone, forming a chemically different material, and typically turns white.
The above pertains to early stone beads from Harappa and Mesopotamia, later similar products made nearly two thousand years later (parallel to Roman times), as recently as Sasanian times (another 500 to 1000 years later)--and was used for Tibetan zi beads (that remain virtually undated). In the early 1990s, Chinese beadmakers figured out how to use this process to make agate reproductions of zi beads. Thus the beads we have discussed in this thread.
It is entirely possible that acid is used as part of the processes that artificially "age" these reproductions. However, let's not confuse the issue by suggesting that the decoration itself is "acid etched." It's not.
Also, the suggestion that there's a dichotomy between smooth new-looking beads and crackled beads is oversimplified. There are lots of different "finishes" on these beads that are intended to make them "look old." Some are done better than others (or are more realistic-looking). It is a poorly aged bead that is cheap. The more nicely aged beads will demand a higher price than a poorly aged bead (because is it an obvious fake), and more that the obviously new (unaged beads) because they are new beads. The well-made beads can be passed off as ancient, and sold for many, many times their true value.
The brown-to-black coloring of zi beads and other later decorated stone beads is derived from a separate group of treatments--but that's a different issue entirely. This should not be confused with chemical decoration, but is better thought of as a sort of "staining" process. All of this is discussed in my article on Tibetan zi beads in Arts of Asia magazine.
Jamey
