| Original Message: Artificially-Colored Agate |
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Hello Christina, I have discussed the topic of artificially-colored agate many times here and at other sites. The enhancement of stones, particularly agates may go back in time to as early as 3000 BCE at the Harappan culture (present day Pakistan). The primary treatments involve heating the stone; soaking the stone in mineral-rich solutions, followed by heating or burning; applying chemical solutions (popularly called "etching" and discussed here just a few days ago), followed by heating or burning. All of these treatments are more-or-less permanent. There are many temporary treatments too, some of which involve dying the stone whatever color is desired. At Germany, colored agate is is referred to as being "beizen" (sounds like "BITE-zen")—meaning soaked in an acid solution (and heated). This should not be confused with temporarily dying a stone. It is believed that the stone works at Idar-Oberstein were developed as long ago as Roman times; and it is recognized that some typical treatments (such as soaking a stone in a sugar solution to make it brown-to-black) were also know in Roman times. But in any event, regardless of how long ago thee practices were introduced to Germans, they became the most proficient and nearly exclusive practitioners of this art well into the 20th century. In the 1980s, these treatments were transfered to Brazil (from where the Germans had been importing agate since about 1880). In the 1990s, the Chinese learned to do this work. (Prior to that time, they were importing German colored agate to Hong Kong, to make such beads.) The most common colored agates are carnelian and "black onyx." Both start out as undistinguished pale or nearly colorless gray, translucent agate (from Brazil). Although most people think these stones "are natural," in fact they are not. The success of these coloring treatments depends on the stone used. It must have "porosity" to accept the mineral baths the stone is submitted to. When the stone is not very porous, the color achieved may be blotchy or patchy, inconsistent, or almost absent. The German agate pendants shown in this thread of messages are just such products. They were intended to be banded carnelian, but didn't take the color well. I have seen hundreds of specimens of such treatments, from out of Germany. In the past, China was a significant producer of carnelian beads. One has only to see the quantity and quality of these beads to appreciate this fact. It has never been determined whether they understood heat-treating agate, or if they had access to excellent sources of natural carnelian (including the beautiful material from which pema raka beads were made for Tibet, and for other beads—including prayer beads). But regardless of Chinese output, the beads of India far outnumber the production of any other region, particularly in antiquity (and particularly if we include the beginnings of these industries, as happened at Harappa). It is a well-known fact that at India, the agate that is gathered from river sources is already rich in iron impurities, and only requires heating to become carnelian. Other chemical treatments are unnecessary. but not all of this material turns out beautifully-red. It likewise may be pale or blotchy. Chinese beadmakers have been temporarily coloring stones for a long time. Easily since the Ching Dynasty, and probably much earlier. One example is quartz beads that have been heated to make them crackle, and are then dyed to add color. The red ones look a lot like tourmaline or even ruby. Fossil walrus ivory has been dyed brilliant green to copy malachite or Imperial jade likewise since the Ching Dynasty (if not earlier). For as long as current Chinese beads have been coming into the States (since ca. 1980), the dying of stones to make them look like "jade" has been routine—particularly for serpentine, but also actual jade (jadeite). As for "records," these were and are secret processes—as are the details of many aspects of art and artifice. It would be unreasonable to expect to find formulas; or it would be fortuitous. But probably the artificial treatment of agate (possibly with the exception of carnelian, sard, and onyx—since these are simple treatments) may have been unknown to China. In point of fact, I believe that many or most of the artificially-colored agate beads now found in China (with the exception of certain generally distributed banded beads from antiquity, common to Tibet and Central Asia), are actually from places like India, Afghanistan, and Burma, and only recently made it into China. (As I have already mentioned.) I have studied these issues since the early 1980s, and didn't come by the information I have easily. It involved considerable research, and viewing thousands of beads—as well as some helpful guidance from Si Frazier (a local mineralogist, and mentor). Zi beads from Tibet are one of my specialties, and it would be impossible to understand their nature if one did not know about the artificial coloring and other chemical treatments of agate. This art made those beads possible. The Chinese apparently made simulants of zi beads over 100 years ago (except using serpentine), so they had some familiarity with the processes—but nothing like what they have developed since about 1993. Jamey All rights reserved by Bead Collector Network and its users |
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