How To Date Diamonds?

Scientists estimate that the earth is about 4.6 billion years old. According to GIA, research published in 2010 indicates that the youngest known diamonds—found in a Brazilian kimberlite—are just 107 million years old. On the other hand, the oldest known diamonds—from Canada’s Ekati mine—are as much as 3.5 billion years old.

Scientists measure the age of a rock with a process called radiometric dating. The minerals in a rock might contain radioactive elements. If they do, those elements give off atomic particles as they decay. As a radioactive element emits its atomic particles, it gradually changes to another form of the same element or to a different element: Scientists call it a “daughter” or end product.

There are several naturally occurring radioactive elements. Each decays at a set rate and forms a specific end product. Scientists measure the end products by chemically separating the radioactive elements from the rock or mineral and calculating the amounts using sophisticated laboratory instruments called mass spectrometers. As long as they know the rate of decay of each radioactive element, scientists can figure out how old the rock or mineral is.

Diamonds themselves can’t be dated: Their radioactive elements decay too fast to be measured. Fortunately, some diamonds contain inclusions with elements that can be dated.

Using radiometric dating of diamond inclusions, scientists determined that diamonds are often much older than their host rock. Diamonds that formed 3.3 billion years ago have been found in kimberlite deposits only 100 million years old. This proves that diamonds can be stored deep in the earth for a long time before being transported to the surface, and also that kimberlites and lamproites are carriers, not formation sources, of diamonds.