Are the curative properties of 'Black Mud' from the Dead Sea due to presence of bitumen (asphalt) or other types of organic matter?

Deep black clayey sediments of the Dead Sea, previously covered with water at times of higher sea level, are being mined for therapeutic purposes and for the preparation of cosmetic products under the name 'Black Mud'. It was claimed that the beneficial properties are due to the presence of bitumen (asphalt) as attested by the colour. Less commonly, the curative properties have been ascribed to humic acids or to organic matter derived from algae in the lake. Asphalt from the Dead Sea has been of major economic importance to the region and was used as a medication for 2000 years until the mid-20th century. Geochemical analysis of the Black Mud showed that it contains relatively little organic matter (ca. 0.6-0.8% organic carbon) and that the organic matter is mostly derived from the land masses surrounding the lake. Asphalt was totally absent and the concentration of humic acids very low. The black colour of the mud is rather due to the poorly crystallised iron sulphides. Based on this, the therapeutic properties of the mud are ascribed to its content of reduced sulphur species, its physical and chemical properties and possibly its brine content, but not to the presence of organic matter.