Photo of the ruby used in this study. Credit: University of Waterloo
Researchers from the University of Waterloo discovered that carbon residue was once part of ancient life in some of the oldest colored gemstones in the world. This carbon residue was found inside a 2.5 billion year-old ruby.
Chris Yakymchuk (University of Waterloo professor of Earth and Environmental Sciences) led the research team that studied the geology and formation of rubies. The team discovered a ruby sample containing graphite during their research in Greenland. This country is home to the oldest known rubies deposits in the world. This carbon is an evidence of the existence of early life.
"The graphite in this ruby is truly unique. Yakymchuk says that this is the first time that we have seen evidence of ancient life in ruby bearing rocks. The presence of graphite gives us additional clues about how rubies formed in this area, something impossible based solely on the color and chemical composition of a ruby.
Researchers were able to use graphite as a means of analyzing a property known as isotopic composition of carbon atoms. This measures the relative amount of different carbon molecules. While more than 98% of carbon atoms have a 12 atomic weight unit mass, a few carbon-atoms are heavier with 13 or 14 atomic weight units.
Yakymchuk stated that living matter prefers lighter carbon atoms, as they require less energy to integrate into cells. We concluded that carbon atoms in graphite had once been part of ancient life. This is most likely due to the presence of carbon-12.
Graphite can be found in rocks older that 2.5 billion years. This is a time when oxygen was scarce and life existed only as microorganisms or algae films.
Yakymchuk and his team found that graphite was not only necessary to create this ruby, but also links it to ancient life. The graphite created favorable conditions for the growth of rubies by altering the chemistry in the rocks. The models of the team showed that it was impossible to form rubies at this location without graphite.
Recent publication in Ore Geology Reviews was Corundum (ruby), growth during the final assembly at Archean North Atlantic Craton. It is located in southern West Greenland. In June, Chemical Geology published a companion study entitled The corundum dilemma: Limiting the compositions fluids involved ruby formation in metamorphic mélanges of ultramafic or aluminous rocks.
More information: Chris Yakymchuk and colleagues, Corundum growth during the final assembly, Archean North Atlantic Craton. South West Greenland. Ore Geology Reviews (2021). Chris Yakymchuk and colleagues, Corundum growth in the Archean North Atlantic Craton's final assembly, south West Greenland (2021). DOI: 10.1016/j.oregeorev.2021.104417 Vincent van Hinsberg et al, The corundum conundrum: Constraining the compositions of fluids involved in ruby formation in metamorphic melanges of ultramafic and aluminous rocks, Chemical Geology (2021). DOI: 10.1016/j.chemgeo.2021.120180 Journal information: Chemical Geology