Discovery of the Earliest Synthetic Carborundum (SiC) in Neolithic Jade Artifacts in Eastern China

Discovery of the Earliest Synthetic Carborundum (SiC) in Neolithic Jade Artifacts in Eastern China

Terrestrial Atmospheric and Oceanic Sciences 25(4):537
DOI:10.3319/TAO.2014.02.21.01(TT)

Abstract
Using Raman microscopy and scanning electron microscopy we have successfully identified, for the first time, synthetic silicon carbide (carborundum) particles in 15 unearthed relics and assorted remains from five out of six Neolithic sites (similar to 4000 - 7000 years b.p.) in Eastern China. Because of its extreme hardness, silicon carbide was apparently employed in the manufacture of ancient jade artifacts presumably as an abrasive for polishing. We show that Neolithic people may have already used this synthetic material to carve and polish both jade and quartz artifacts, contributing to the blooming development of the jade culture throughout ancient China.

4. DISCUSSION
How did the ancient Chinese develop SiC as a polishing abrasive material? Moissanite is extremely rare as a naturally occurring mineral, so it is impossible to find and collect large quantities of moissanite in nature. However, carborundum may be produced naturally in common pottery-firing processes, when natural fuel, such as grass, wood or coal comes in contact with natural mineral quartz or sand. For example, sample No.1 clearly shows the co-existence of both SiC particles and wood-ash. Although the ancient processes were probably very crude and difficult to control, and the quality of the products was likely to be inconsistent, the process was easy to implement, even for the Neolithic tribes in Eastern China. In addition, eleven other samples of category I (not listed in Table 2) collected near sample No. 1 at Lingjiatan, all show the existence of SiC particles.

The discovery of this study, contrary to known history, pushes back the age of the first known synthetic SiC by several thousand years, to the Neolithic age. We may never know for sure whether the ancient people made SiC accidentally or on purpose. We do know, however, that Neolithic tribes in Dingshadi (now in Jiangsu Province) had successfully synthesized carborundum (sample No. 14) as early as 7622 years b.p. (Fig. 3d and Table 3). Furthermore, the existence of SiC is widespread, as evidenced from the unearthed relics in five out of the six Neolithic sites investigated (Table 2). The evidence from category IV and V SiC samples, which were collected directly from the surfaces or holes within tools or jade artifacts, suggests that the tribes in Lingjiatan had broadly adopted SiC for carving jade as early as 5453 - 5599 years b.p. These groups are thus likely to be the first known humans to have employed synthesized polishing abrasive materials in the manufacture of jade artifacts. It is apparent that “SiC technology” also spread to the Liangzhu culture (~5600 - 4000 years b.p.) (He 2005b), helping it to become the most prosperous and prolific jade cultural period in Neolithic times in China. Although there has never been a historical record about the kind of grinding materials used for jade processing, we suggest that the SiC technology could have had a profound influence on the subsequent development of jade culture in China.

As mentioned previously, the Dingshadi tribes of Eastern China manufactured carborundum as early as 7622 years b.p., although they did not seem to know how to use it in the production of jade artifacts. People in Lingjiatan in Anhui (~5453 - 5599 years b.p.) likely improved on carborundum production while firing pottery, to produce greater amounts of carborundum for carving jade and other hard stones. Note that in order to carve and polish so many delicate jade artifacts, they would also have had to develop techniques to concentrate the minute amount of SiC particles spread throughout the pottery clay, although it remains unclear how this was accomplished. In a broader context, the results of this study may indicate the earliest use of synthetic abrasives in human history. At ~5453 - 5599 years b.p., the Liangzhu culture adopted the technique, which they very likely inherited from the Lingjiatan culture. Under the Liangzhu culture, one of the most prosperous and prolific periods of jade production and culture in China’s history, jade production bloomed and this development had a profound influence on the future development of jade culture in China. This study shows very strong evidence that the proliferation of jade culture in China likely had its roots in the serendipitous discovery of how to synthesize carborundum by Neolithic tribal peoples about 7622 years ago.