Ubiquitous moissanite (SiC) ‐ from Earth's surface to core: insight through experiments and studies of natural samples

Moissanite (SiC) is an important mineral of the carbides group for understanding crust-mantle processes of silicon and carbon interaction during deep subduction of continental material into the Earth’s interior. The carbon cycle involving carbides (SiC and FexCy) has potentially significant implications for the study of early life on Earth. Moissanite was found in meteorite impact craters, as inclusions in kimberlitic diamonds, kimberlites and mantle xenoliths and was traditionally considered as a high-pressure mineral, though over the last decade, a number of publications have been devoted to new findings of SiC in chromitite from ophilolite formations and in other magmatic, metamorphic and sedimentary rocks with suggestions of lower mantle origins; or, alternatively, suggestions that SiC may have formed in the shallow Earth. In the 1960s-70s, there were inexplicable reports of findings of SiC in pegmatites, granites, sedimentary rocks, and in polymetallic deposits in the former USSR. Those SiC samples, however, were found only in heavy mineral separates, and therefore the relation of the SiC with other minerals remained uncertain and requires further re-examination. The most common feature for terrestrial SiC is that although its formation requires extremely reduced conditions of 4.5-6 log units below the IW fugacity buffer, it occurs in many cases within highly oxidized phases.