Finding a diamond mine may soon become a little easier — thanks to a surprising clue hidden inside an ordinary mineral. Researchers at the University of Alberta have discovered that tiny amounts of water trapped within olivine crystals can help geologists predict whether underground volcanic formations are likely to contain valuable diamonds. The revelation could save diamond explorers millions of dollars by helping them identify promising deposits before committing to costly drilling and testing.



The discovery, published October 22 in the journal Nature Communications, focuses on the relationship between olivine, water and the extraordinary journey diamonds take from deep inside the Earth to the surface.

To understand why this matters, it helps to know a little about kimberlites. These unusual volcanic rocks originate deep within the Earth, where natural conditions allow diamonds to form. When kimberlite magma surges toward the surface, it can carry diamonds along for the ride, delivering them into deposits that may eventually become mines.

The catch is speed. Diamonds can be damaged or dissolve if the rising magma takes too long to reach the surface. A fast ascent gives them a better chance of surviving the journey intact. Unfortunately, determining whether a particular kimberlite rose quickly enough — and preserved enough diamonds to make mining worthwhile — has traditionally required expensive exploration work.

That's where olivine comes in. One of the most abundant minerals in kimberlite, olivine can retain tiny traces of water within its crystal structure. Researchers found that olivine containing more than 40 parts per million of water is associated with kimberlites that have higher diamond grades. The water acts like a geological speedometer: crystals that retain more water provide evidence that the magma rose rapidly, helping protect its precious cargo. Slower-moving magma allows hydrogen to escape from the crystals and may give diamonds more time to deteriorate.

The practical advantage is substantial. Instead of immediately extracting hundreds or thousands of tons of rock to estimate a deposit's diamond potential, exploration teams can analyze small samples of olivine using a technique called infrared spectroscopy. The relatively inexpensive test measures the mineral's water-related signature, giving geologists another tool for deciding which discoveries deserve further investment.

Although thousands of kimberlite formations have been discovered worldwide, only a small fraction contain enough recoverable diamonds to justify the enormous expense of developing a mine. Estimates commonly put the economically viable share at less than 1%. A reliable early warning that a deposit is unlikely to be productive could therefore prevent millions of dollars from being spent pursuing an unpromising target.

The researchers emphasize that the water content of olivine is a complementary indicator, not a guarantee of a profitable diamond deposit. Nevertheless, the finding adds a valuable new clue to the exploration process.

Credit: Image by Parent Géry, CC BY-SA 3.0, via Wikimedia Commons.