Have you ever heard of ice-VII? Probably not. Did you even know there were different water ice phases? Again, it wouldn’t be surprising if you have not. So, why are we talking about it? You might be thinking: “Why is a jewelry store writing about water ice?” We get it- it’s very scientific. But it’s actually a pretty cool new discovery, and it relates to diamonds! And we’re obviously very intrigued by all things diamond-related. Most diamonds are for people who love the glitz and glam of diamond jewelry. Others are for scientists who are looking to expand their knowledge about the Earth’s interior. But when you have a true appreciation for diamonds, they are admired for both reasons! We usually focus on the outside appearance of a diamond- the way it sparkles and catches the light, the way it looks set in jewelry, how many carats it is- but right now, we’re going to focus on the inside of a diamond.

Understanding Diamond Formation and Ice-VII

Now, we’re not scientists so we’ll try to make this as easy to understand as possible. We all know diamonds form deep in the Earth’s crust under intense pressure and extreme temperatures. But what you might not have realized is that during their formation process, diamonds can encapsulate bits and pieces of the chemical environment (water, minerals, etc.) around them. These are called inclusions. If you’ve heard of inclusions before, you understand these are natural flaws that require high magnification to be seen.

So, what does this have to do with Ice-VII?

Well, here’s where it gets pretty nerdy. Diamond inclusions are unique- the material that becomes trapped inside them during the formation process remains under the same pressure as when it was first encapsulated. This is why diamonds are such useful clues as to what’s hidden deep within the Earth’s mantle. However, Ice-VII is different from every other phase of water ice. When normal ice, ice-I, is compressed, its structure changes and becomes ice-II. Adding more and more pressure to the ice will cause it to transform into ice-III, IV, V, VI, and then VII. But Earth’s mantle is too warm for Ice-VII to even exist. So how was it discovered? As we know, diamonds can trap very dense pressurized water during formation. What this new discovery by Oliver Tschauner and his team shows is this: while the diamond is moving up through the mantle, the water inclusion is subjected to cooler temperatures, but it remains under the same pressurized conditions from deep within the mantle. In these very specific circumstances, Ice-VII forms.

Why does this matter?

It may not seem like an astounding discovery, but it actually is. According to Science, Ice-VII is the first evidence of aqueous fluid in the Earth’s mantle. Before this finding, it was believed this particular ice phase did not naturally occur on Earth. Scientists believed ice-VII was only found in the solar system, like in ice moons. But now we know that it can form on Earth, and that’s a pretty cool discovery. So, who knows? The next time you purchase a diamond, it may contain Ice-VII inclusions. And that’s pretty rare.