Occurrences of two new types of gem deposits in Okkampitiya gem field in Sri Lanka

Abstract

Two new types of gem deposits have been discovered recently in Okkampitiya gem field which is situated in south eastern Sri Lanka. These are (1)the gem bearing sediments enclosed within karstic pothholes and channels in marble (2)a promary hesonite deposit in a cal silicate rock. Dissolution of marble by meteroric waters, particularly along joints and fractures and perhaps sussidence and collapsed may have formed the potholes and cannels. Subsequently these karstic features may have trapped the alluvial sediments. the physical and chemical properties of the hessonite are similar to pure grosullar garnet. It is suggested that the hessonite-bearing calc-silicate rocks was formed during the granulite grade metamorphism of marl rich in grossular forming components.