where it is found that all metals higher release. It is also interesting to note that the release of Cr from both original Oil Shale and Oil Shale ash obtained at 950 ̊C are lower than that obtained at Oil Shale ashes obtained at 550 ̊C and 750 ̊C. This could be related to the fact that Cr in the first instance are fixed with the crystalline structure of the mineral phases, whereas, it could available for leaching in a matrix obtained at moderate ashing temperatures where better chances to find easy leachable amorphous phases. Never less