Overview

Diamond is a valuable mineral not only for its delicate beauty but also for its scarcity and resistance. It’s forged under the enormous pressure of the underground layers of the Earth’s crust. Lonsdaleite, on the other hand, is a mineral similar to diamond, but of extraterrestrial origin. A new study claims to have found the largest crystal yet of this mineral that is tougher than diamond.

The science and other stuff to know

In a study recently published in the journal PNAS, the authors suggest a plausible explanation for the formation of a lonsdaleite crystal found in a meteorite that may be a remnant of a collision between a small inner planet and an asteroid billions of years ago, when the solar system was in one of its initial stages of formation.

This mineral is curious because its molecular structure —the scaffolding that supports it— is hexagonal, instead of cubic, as is the case with diamonds. This could give the alien crystals greater hardness than their cousins. Both structures are forged under titanic pressures. While the weight of the Earth’s crust crushes carbon into diamonds, it may have taken a colossal event, such as the destruction of a planet by an asteroid collision, to mint lonsdaleite.

The first sample of lonsdaleite was found inside a crater in Devil’s Canyon in Arizona in 1967. The only available samples are those found in craters caused by meteorites that hit the Earth; however, they have even been created in a laboratory by firing graphite disks at a wall at speeds comparable to an asteroid impacting a planet.

“This study categorically demonstrates that lonsdaleite exists in nature.” co-author Dougal McCulloch told CNET. In the study, they used electron microscopy techniques to verify and reach the conclusion that this extraterrestrial diamond exotype was forged thanks to the enormous pressure produced by a planetary collision.

However, the team believes that the widely held belief that diamonds form during the impact may be incorrect, and that the diamonds may have formed at lower pressures after the destruction instead. For example, under controlled conditions, similar processes are used to produce materials for certain metals, semiconductors, and other products.

So what?

“We really don’t know how hard lonsdaleite is. It has been mathematically estimated to be 58% harder than diamond, but that hasn’t been proven by measurements yet,” co-author Andrew Tomkins told CNET.

Knowing the mechanisms that give rise to this type of structure could have repercussions in various areas of knowledge: provide us with information to improve and complete our current model of the formation of the solar system, and allow us to advance in technology thanks to the use of these materials at an industrial level, among others.

What’s next?

The industrial applications that most intrigue experts are related to ultra-hard machinery parts, similar to those that use diamonds. Tomkins stated that in future efforts, they intend to develop an industrial process by which they can replace graphite pieces —a similar material from the diamond family, but less resistant and more abundant— with lonsdaleite. Moreover, the material might be useful in mining as well.