Inclusions found inside diamonds may not be the jeweler’s favorite part of the gemstone. However, scientists are especially interested in a diamond’s imperfections. These inclusions often hold the key to what lies hundreds of kilometers deep underground.
A group of scientists was studying imperfections in earth mined diamonds only to find something strange within the crystal structure. The results were shocking as the scientists discovered that the tiny grain was actually a previously unknown mineral.
The new mineral was named goldschmidtite (K,REE,Sr)(Nb,Cr,)O3 . The goldschmidtite inclusion is about the width of a human hair at 100 micrometers and has a dark green color. Scientists have stated that it has unusual chemical properties and the diamond did a good job of protecting the mineral over millions of years thanks to its hard crystal lattice.
The team from the University of Alberta, Glasgow University and Northwestern University discovered the grain of goldschmidtite inside a dodecahedral diamond. The grain has a density of 5.32g/cm3.
The diamond containing the new mineral was mined in the Koffiefontein pipe in South Africa which is managed by Petra Diamonds and is known for producing some of the finest diamonds in the world.
Nicole Meyer, a Ph.D. student at the University of Alberta said, “Goldschmidtite has high concentrations of niobium, potassium and the rare earth elements lanthanum and cerium, whereas the rest of the mantle is dominated by other elements such as magnesium and iron”.
The tiny spec trapped inside the diamond was encompassed by the diamond structure as it was forming around 105 miles under the surface. While inclusions are nothing new, this one was particularly special as it showed the composition of the surrounding rock at such depths.
Back in 2014, a team of scientists discovered hydrous minerals inside a mined diamond. This was evidence that there was water hidden and locked deep within the earth’s mantle.
Mantle geochemist Bryan Pearson said, “goldschmidtite is highly unusual for an inclusion captured by diamond and gives us a snapshot of fluid processes that affect the deep roots of continents during diamond formation”.
What’s more, the process involved in forming the mineral itself must have been quite unique. The major elements are potassium and niobium and the fact that they are rare means that the mineral formed under intense and exceptional geological and chemical processes.
Scientists decided to name the rare mineral after the famous mineralogist of the late 19th and early 20th century Victor Moritz Goldschmidt. Victor was the first to research the chemistry of the perovskite crystal which is similar in crystal chemistry to the newly discovered mineral.
“There have been several attempts to name new minerals after Goldschmidt, but previous ones have been discredited. This one is here to stay”, said professor Pearson.
Goldschmidite is chemically similar to potassium niobite, a perovskite structured crystal with a chemical formula of KNbO3. However, what makes it so special is its unique structure and is the fifth known perovskite mineral found in the earth’s mantle.
Now that scientists have identified the mineral, the next step is to create a model on how the mineral formed deep underground. The team doing the research will be searching for more samples of goldschmidtite in the Koffiefontein pipe to find out whether there are variations of the mineral.
The rare goldschmididte mineral is now stored at the Royal Ontario Museum in Toronto.