Source: Nature: "Diamonds"
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Unlike most other rocks that are formed in Earth's crust, diamonds are formed deep beneath Earth's surface. Their ability to reveal the chemical and mineralogical nature of Earth's mantle makes them a valuable resource for geologists seeking to uncover the many mysteries of Earth's interior. However, the task is challenging due to the diamonds' tight internal bond, which makes the stones difficult to date. In this video segment from Nature, geologist Larry Taylor explains the geological value of diamonds.
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Diamonds are minerals that are valued for their durability, beauty, and rarity. They form deep in the earth under conditions of extreme heat and pressure, and are brought to the surface of the earth by the forces of volcanism and weathering. Generally, diamonds - and the rocks they’re found in - are very old. Studying diamonds, therefore, can help scientists reconstruct the processes that were central to the formation of the earth itself.
The physical properties of a diamond are determined more by the crystal structure of the diamond than by its composition - consider that diamond and graphite, despite their vastly different physical properties, are both composed of pure carbon. Every mineral is characterized a particular type of crystalline structure that is largely responsible for its physical properties.
Diamonds are not forged in the earth’s crust where most other rocks are made. They come from much deeper, from a hundred miles within the earth’s interior. And occasionally, in bursts of intense violence, this buried treasure rockets to the surface, carried by special, high-speed volcanoes.
To geologist Larry Taylor at the University of Tennessee, diamonds are a treasure trove – but not because of their beauty.
Lt: This is the only hard samples we have of the deep interior of the earth. The diamonds are telling us something, they’re telling us a story. So it’s understanding the story that’s being told by these minerals which is at the key to all our understanding, our knowledge about the earth.
Lt: We, we consider ourselves geologic detectives. We’re trying to recreate the crime after the fact. We look at the diamonds and we’re trying to figure out exactly how they formed, where they formed, why they formed.
But the diamonds, themselves, reveal very little. Even their age has been a source of scientific controversy. Most rocks and minerals can be dated because they contain certain radioactive atoms. As these atoms decay, they reveal their age.
But diamonds never decay. Their chemistry is so stable, their internal bonds so tight, nothing inside the diamond changes. A diamond never grows old.
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