Gold and Other Metals in Graphite

Graphite, as a pure form of carbon, is found in Sri Lanka as disseminated flakes and in veins. In veins found in high grade metamorphic rocks, graphite often attains 99% purity. A variety of metals are found to accumulate in the graphite, mainly at the margin of these veins. Gold, in particular, becomes concentrated at vein margins, suggesting a hydrothermal transport mechanism and accumulation by carbon. It has been postulated that graphite becomes activated at the vein margins under high temperature conditions and it is this activation that provides sites for the accumulation of metals. Graphite has been reported from hydrothermal vents in the sea floor and these are associated with sulfides, particularly those of antimony. Even though the origin of graphite is still being debated, a deep-seated carbon source and metal-rich solutions appear to play a major role in the accumulation of metals in vein graphite.