Diamagnetism of natural fullerene-like carbon

Carbon from shungite rocks from Karelia (Russia) displays an increase in diamagnetism between ca. 90 and 150 K. The diamagnetic effect is largest for samples that contain twisted graphene layers up to 100 nm across, preferentially oriented, and with nanometer-sized pores as seen in high-resolution transmission electron microscopy images. No increase in diamagnetism was observed for shungite rocks containing carbon with randomly oriented graphene layers. Such diamagnetism has been observed for doped fullerites but has not previously been reported for amorphous natural carbon.