An Earth's crust 2.5 million years old, a ruby contains evidence of early life. It wriggled around in Earth's mud.
Geologists discovered graphite, a form carbonate that is pure and unadulterated, in the precious stone. They believe this to be biologically derived, and the remains of an ancient microorganism.
"The graphite in this ruby is truly unique. "This is the first time that we have seen evidence of ancient life in ruby bearing rocks," stated Chris Yakymchuk, a Canadian geologist.
"The presence graphite gives us additional clues about how rubies formed in this area, something impossible to directly determine based on a ruby’s color or chemical composition.
The mineral corundum, a crystalline form aluminum oxide, is used to make rubies. It forms when it is subject to intense heat and pressure at Earth’s tectonic borders, where tectonic collision and subduction create the required environment. The presence of rare element chromium gives the stones their deep color. The more chromium in the gem, the deeper the hue.
As with all minerals, the purity and clarity of rubies varies. Precious gems can contain impurities or inclusions due to their formation process. These stones might not be suitable for jewelry but are great for science.
A mineral that was thousands of kilometers beneath the ground and which would not have survived on the surface was preserved in a diamond. A deeper understanding of the process by which tectonic subduction can cause surface minerals to sink downwards was possible thanks to surface minerals discovered in another diamond. (There was also another diamond in the diamond. But that's cool.
Yakymchuk and his colleagues were trying to understand the processes of corundum formation by studying rubies from Greenland. This is where one of the oldest known deposits of the mineral. They discovered the graphite inclusion while studying these samples.
Graphite may form abiotically through chemical or mineral processes. However, it can also serve as a biomarker. You can determine the carbon isotope to distinguish the difference. These are forms of the same element that have different numbers of neutrons and thus different atomic masses.
Carbon-14 is a radiocarbon that can be used to date physical artifacts. It forms abiotically in the Earth's atmosphere. Carbon-12 is the lightest natural stable carbon isotope on Earth. It is also found in living organisms.
The team discovered that the graphite found in the ruby contained carbon-12. This is consistent with an organic origin. The researchers were able to determine the origin of the organic origin because they knew the age of the gem. Life on Earth 2.5 billion year ago was very limited.
Yakymchuk stated that living matter prefers lighter carbon atoms as they require less energy to integrate into cells.
"Based on the higher amount of carbon-12 found in graphite, it was concluded that carbon atoms once belonged to ancient life. It is most likely that they were dead microorganisms like cyanobacteria."
This gave rise to clues about how rubies might have formed. Too much silica can cause corundum to form.
The presence graphite indicates that there was a fluid that helped to transfer silicon dioxide from the rock. This would have been the catalyst for corundum formation.
The research was published in Ore Geology Reviews.