Naturally occurring fullerenes have been found in rock samples that were subject to singular geologic events such as lightning strokes ( 1 ) , wildfires at the K-T boundary ( 2 ) , and meteoritic impacts (3). These findings are expected, as fullerenes form normally under highly energetic conditions. However, P. R. Buseck et al. (4) reported the presence of C60 in a carbon-rich rock sample from Shunga, in Karelia, Russia. in which the host geologic unit was highly metamorphosed and there was no evidence of exposure to extreme conditions. If fullerenes did form naturally in such an environment, we would expect them to be widely present elsewhere, and there would be many ramificatlons. For example, the presence of fullerenes in the earliest times would have implications for the evolution of life (that is, as an early source of large molecules).
We studied the occurrence and distribution of fullerenes in carbon-rich rocks, including samples of shungite from the deposit in Shunga.