Tuesday, April 9

Space gems: a Universe full of diamonds, rubies, sapphires and emeralds


Diamonds that fall to earth in meteorites and that rain down on Neptune and Uranus, opal on Mars, planets abundant in rubies and sapphires, even the core of a star!, which could be made of diamonds, as well as gems that do not exist on our planet, like the peridot stone that arrives in pallasite meteorites from outer space.

Is this a fantastic medieval tale of lands (albeit far away, in other solar systems or galaxies) teeming with riches for the bold who face danger and riddles until they get the promised treasure? No, they are the conclusions of scholars of the Universe who, analyzing the composition, density and luminosity of various celestial bodies, are convinced that they are real possibilities. To understand it, you have to know what they are or how we define gemstones and how they are formed on our own planet.

The definition of ‘precious stone’ is not based, however, on any geological or chemical reality, but on the human being’s appreciation of beauty. There are elements that make a mineral be considered as such: its beauty, its scarcity and its ability to be carved, that is, turned into a gem to create jewelry such as crowns, bracelets, rings and necklaces. By the traditional definition, there are only four gemstones: diamonds, rubies, sapphires, and emeralds. All the other minerals that we use as adornments in jewelry are semi-precious stones, such as opal, turquoise, aquamarine, amethyst and pearl, which is not a mineral but an oyster secretion, but is included as such because of its jewelry value.

The origin of precious stones

The queen of precious stones is, without a doubt, the diamond, because its scarcity was such that until the 19th century it was reserved for the richest and most powerful, although since then its mining has made it less exclusive. Today we know that diamond is a very common mineral and we can all buy it. For example, an emery with diamond powder for DIY. Diamonds for jewelry are still rare, but are becoming less rare.

Diamond is simply a crystallized form of carbon, as is mineral carbon, graphite. Carbon is the basis of life on our planet and as such is very abundant, so much so that in the form of carbon dioxide it is one of the causes of climate change. Diamond forms under high pressures and temperatures. The ones we can recover from the earth are over 3 billion years old and were formed in the Earth’s mantle and not from coal (whatever the Superman comics say).

Rubies are a variety of corundum, which is nothing more than a crystalline form of aluminum oxide with small amounts of chromium that give it its blood-red color. Interestingly, the other gemstone, sapphire, is also crystallized aluminum oxide, but with small amounts of iron, titanium, chromium, vanadium, or magnesium. They are created under extreme conditions of heat and pressure deep within the Earth. When compressed, the oxygen and aluminum atoms crystallize forming corundum, which is a colorless mineral that can take on different colors depending on the impurities it contains.

diamonds at your feet

  • A thin layer of nanodiamonds.
    In 2007 it was announced that a thin layer of nanodiamonds distributed over three continents had been discovered, probably the product of a comet crashing into our planet just 13,000 years ago, which would have been responsible, among other things, for the extinction of the megafauna in the northern hemisphere and the disappearance of the Clovis culture in North America.

Emeralds, on the other hand, are formed in igneous rocks from beryl, which is a mineral made of silicon, oxygen, beryllium and aluminum and that takes on its striking green color by containing small amounts of chromium or vanadium. If in its composition there is iron instead of these two elements, it is the semi-precious stone called aquamarine. They can be formed with hydrothermal fluids from the depths of the earth’s crust that contain the elements of emeralds, in particular beryllium, rise to higher layers and, when cooled, create veins in which emeralds are formed through a slow process of crystallization. In another process, they are formed from the magma that comes from the depths and cools, crystallizing as well.

Recreation of the white dwarf BPM 37093, with its diamond core. /

HARVARD UNIVERSITY

Knowing this, it becomes clear that, as Stanford University Geological Sciences Professor Wendy Mao says, “we can form all kinds of gems in space, as long as you have the right chemistry at the right temperature and under the right conditions.” .

The predictions of the researchers of the Universe is that planets in other distant solar systems could be full of rubies and sapphires, and even zirconia, that cheap (but beautiful) copy of diamonds. But Mao herself warns that most of the precious stones from outer space will hardly have quality to be used as gems, because the creation of those large crystals that provoke our admiration usually requires liquid water, so that in places where there is not this, there will not be.

the diamond star

About 50 light years from our planet is the star BPM 37093 (also called V886 Centauri because it is in the constellation of Centaurus, seen from our planet). It is a star of the so-called ‘white dwarfs’, which are the final stage of the so-called ‘main sequence’ stars like our sun, which in about 10,000 million years will also become a white dwarf. Having run out of hydrogen for fuel, these stars have fused helium in a process called ‘triple alpha’ until they are made up mostly of oxygen and carbon.

In the 1960s, a group of astronomers proposed that as a white dwarf cools, given the enormous pressures at its center, its material will crystallize. And, if the star experiences pulsations, we can study these to derive information about its structure. On these bases, since 2004 it has been calculated that the core of BPM 37093 must be between 32% and 90% crystallized. And crystallized carbon is, of course, diamond, so this star could contain the largest known diamond.

Scientists then gave this star the name ‘Lucy’, after the Beatles song ‘Lucy in the Sky With Diamonds’. But this is not the only relationship of this possible star diamond with popular culture. Lucy has been a part of Jim Jarmush’s film ‘Only Lovers Left Alive’, John C. Wright’s novel ‘Count to a Trillion’ and the webcomic ‘Abstruse Goose’.


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