Bertrand Devouard: “A rather rare discovery” on “a rather extraordinary meteorite”
Is such a discovery exceptional?
This is relatively rare: in total, about fifty minerals must be discovered per year. Which may seem like a lot, but when you compare that number to the millions of living species… What’s particularly interesting here is that they came from a pretty extraordinary meteorite itself: a 15-ton stone , known to local people in Somalia for generations, but was only identified as a meteorite two years ago.
And it is a particular meteorite…
Indeed, it is a meteorite that we do not understand well. In general, iron meteorites are considered to arise from the remains of ancient cores of fragmented planets. But we do not know many meteorites of the group of this one: one hypothesis is that it would come from a core in the process of formation, with many inclusions of other minerals. These meteorites are quite conducive to the discovery of minerals unknown on Earth.
Why ?
Because they have what are called “redox states”. It’s a bit technical, but on Earth, there is oxygen almost everywhere, except in the core. Also, most of the elements are bound with oxygen. In meteorites where there is a lot of iron in the metallic state, it is more complicated. These are conditions that we do not know on Earth, where iron in the native state practically does not exist. So these very particular conditions give rise to these assemblies which can form these extremely original minerals.
How do you define a “new” mineral?
A new mineral is very well defined: it is an original composition of one or more chemical elements with a crystal structure unknown until now. Just as graphite and diamond are both made up of carbon atoms, but arranged differently. They are two minerals that have the same chemical composition, but their particular structures give them completely different properties.
Do we already know what these discovered minerals are made of?
Yes, these are two rather original iron phosphates. New minerals are something that is very well framed at the international level: there are a working group of the International Mineralogy Association who will appraise them and officially accept them after discussion.
In concrete terms, what “use” these discoveries?
Sometimes I answer “like a Beethoven symphony, nothing! But more seriously, what also characterizes a mineral is that it is found in its natural state – even if these had already been synthesized in the laboratory. And in general, it is useless in itself, but it can give ideas to chemists. Phosphates are for example widely used to possibly make more efficient batteries. They will therefore perhaps find an application in the long term. All this remains hypothetical, as is often the case in fundamental research, it is the beauty of science.
But any new chemical compound can be interesting for its properties: a few years ago, a French laboratory had synthesized a rather complex compound. Shortly after, a Japanese team discovered that it was superconducting. And that, today, is widely used in medical imaging, etc.
Do we always know how to synthesize minerals?
No: sometimes it is extremely difficult and it is not an issue when there are no particular properties.