Raining Diamonds: Gemstones that are out of this World

Raining Diamonds: Gemstones that are out of this World

Quality diamonds, rubies, sapphires, and similar precious stones are rare on Earth. But in space? Not so much. One of the scarcest stones on Earth, the brilliant diamond, may be ubiquitous in this galaxy. In fact, it may be common in our solar system. On Neptune diamonds are so common that they literally fall from the sky as rain. Well, sort of.

Mineralogy in space is a strange field that is hindered by some technical limitations. Scientists have to rely on complex mathematics, probes, satellites, and really good guesses to substantiate accurate theories, but ultimately we can’t truly know what the cosmos has in store for us. 

For now, we can appreciate what predictions we have such as the raining diamonds or planets that are made out of rubies and sapphires.

Raining Diamonds

For several decades, the consensus of scientists was that diamonds were raining on Neptune. Since we don’t have anything to explore Neptune’s atmosphere with (yet), this was only a hypothesis. That was until a laboratory study managed to replicate the hypothesis. It may seem strange that a laboratory recreated the atmospheric conditions of a far-flung planet in our solar system, but it did happen. Well, kind of.

The lab used a specialized tool to create powerful shockwaves that, after touching, generated immense heat and pressure. Carbon atoms in the tested plastic turned into diamond in about a billionth of a second. The effect on Neptune is permanent of course, but this short experiment gives credit to the theory that is difficult to verify.

10k Yellow Gold & White Diamond Cocktail Ring

Neptunian diamonds are probably larger than the ones on Earth. In fact, it is theoretically possible that Neptune has giant blocks of diamond floating in an ocean of liquid carbon, much like Earth’s icebergs that float on water. This is because the solid diamonds in the atmosphere sink to Neptune’s core and collect in a pool of solid and liquid carbon in a separate layer on the planet. It is possible, however, that the diamonds sink and turn into liquid carbon from the intense heat. There is also the possibility that it is nothing but diamond in this carbon layer. We can’t be sure, but all are fascinating possibilities.

Sadly, Neptune is not special in this regard. It has been postulated that Uranus is another planet with diamond hailstorms. Perhaps it is not a coincidence that the two ice giants, or planets with high concentrations of hydrogen and helium. Their water, ammonia, and methane are icy. While they may not be jötunn, they are cold, distant giants.

Worlds made out of Diamond

Not every system is like ours. Some have two stars, only a couple planets, or even black holes. Even in systems like ours with one star that multiple planets orbit, things can change drastically. Of importance is the star which can vary in size, mass, and content. Stars with more carbon to oxygen can foster the development of carbon planets. Carbon planets are, as the name implies, have high quantities of carbon. Carbon is the sole element of diamonds and thus more of it can help produce diamonds. But two more factors are needed: heat and pressure.

Diamond Earth

While other carbon planets will likely have diamonds beneath the surface, 55 Cancri e is a well-known candidate. The planet has been the subject of various studies and reports indicate that it could be an archetypal “diamond planet.” Unfortunately, even if we could get there it would be difficult to extract any diamonds. The surface could be covered in lava oceans, has high radiation, and the atmosphere (if it even exists) is most likely volatile.

These draconian conditions have not prevented scientists from trying to replicate them to test the validity of the diamond planet hypothesis. By immersing silicon carbide in water and applying heat and pressure, scientists produced some glinting diamonds. It seems plausible that carbon planets have rich diamonds below the crust.

Ruby Storms

Just about everyone is familiar with the Great Red Spot on Jupiter. The violent storm continues to rage on. Its color is reddish, like a ruby, but it has little else to do with rubies. However, there is a Jupiter like planet that has storms that may fling rubies and sapphires through the sky. 

Over one thousand light-years away, HAT-P-7b is a massive, stormy planet. The clouds of this giant are made out of corundum, the mineral that makes up rubies and sapphires. This dazzling planet is also the first planet to have known weather systems outside of our Solar System. A great find for future astro-lapidaries and today’s scientists, it is one of the most fascinating discoveries within the last few years.

There is the possibility that its clouds are not made out of corundum. In this disappointing scenario, the clouds would instead be made out of perovskite, a mineral consisting of calcium, titanium, and oxygen. Because titanium is rarer than aluminum (an element of corundum) it is not as likely that the clouds will be made out of this slightly less appealing mineral.

Star Ruby Gemstones Polished

Ultrahot Jupiters, planets that are scorching hot (thousands of degrees Fahrenheit), exhibit strange chemical properties. Despite their heat, they can have water. The tidally locked ultrahot Jupiters seem to do this in a cycle. On the hot side of the planet, the heat sunders the molecules apart. These molecules are then blown to the cooler side where it is perpetually night and form into something new, including water.

They can also form into corundum and titanium oxide. There is a chance that rubies, sapphires, and liquid metal rain from the sky before drifting into the hot side where they are once again reduced to simple molecules.  This cycle practically repeats indefinitely.

Super-Earths (a description o their mass and type, not habitability) could have deep caverns rich with sapphires and rubies too. In fact, they could possibly have gemstones in general. The “hot super-Earths” are the best candidates for these glittering troves of stone. Unlike their bigger, gaseous cousins, these planets would not have clouds that rain rubies.

Opal, Water, and Why it all Matters

Gemstones, as pretty and gorgeous as they are, are not just commodities. We like to put them in rings, necklaces, earrings, and bracelets, but they have purposes outside of jewelry and looking nice on our nightstands. For the scientist, they can be glimpses into the past. Take opal instance.

Opal, a colorful crystal, requires water to form. Water seeps into the ground with silica and evaporates over time. When the water is all but gone, the remaining silica wedged between sedimentary rock forms opal.

This spectacular crystal was recently found on Mars. Even if no other sources or signs of water (either today or in the past) were found on Mars, this discovery would be major evidence for many hypotheses. Opal is still a noteworthy discovery in Martian history, but by the time it was found scientists have already speculated that the planet had water at one time. But today, the nature of opal’s formation might help us discover water on other planets or moons.

Australian Opel Set in a Sterling Silver Ring

You can apply this to every gemstone on other planets. Gemstones and many minerals are pretty for us, but crucial evidence for scientists and useful resources for industry. As resources on Earth dwindle, the notion of interstellar prospecting is becoming less sci-fi and more real with every passing day. There are legal, ethical, and physical constraints but the new space race may be to mines, not to Mars, in the near future.  There may be unforeseen consequences that nobody will know until it’s too late.

But for now, enjoy the ruby rain and fluid sapphire streams on far-flung planets in the Milky Way.


Arbesman, Samuel. The Half-Life of Facts: Why Everything We Know Has an Expiration Date. Penguin, 2012.

Cofield, Calla. “Water Is Destroyed, Then Reborn in Ultrahot Jupiters.” Exoplanet Exploration: Planets Beyond Our Solar System, 24 Sept. 2020, exoplanets.nasa.gov/news/1518/water-is-destroyed-then-reborn-in-ultrahot-jupiters.

Crew, Bec. “Clouds Outside The Solar System Are Made From Ruby And Sapphire Minerals.” ScienceAlert, 13 Dec. 2016, www.sciencealert.com/clouds-outside-the-solar-system-are-made-from-ruby-and-sapphire-minerals.

Kooser, Amanda. “Scientists Investigate Diamond Planets ‘Unlike Anything in Our Solar System.’” CNET, 14 Sept. 2020, www.cnet.com/news/scientists-investigate-diamond-planets-unlike-anything-in-our-solar-system.

Kraus, Dominik. “On Neptune, It’s Raining Diamonds.” American Scientist, 16 Aug. 2018, www.americanscientist.org/article/on-neptune-its-raining-diamonds.

Landau, Elizabeth Nasa. “Lava or Not, Exoplanet 55 Cancri e Likely Has an Atmosphere.” Exoplanet Exploration: Planets Beyond Our Solar System, 25 Sept. 2020, exoplanets.nasa.gov/news/1471/lava-or-not-exoplanet-55-cancri-e-likely-has-an-atmosphere.

“Outer Space Is a Treasure Chest of Gemstones.” Astronomy.Com, 8 Feb. 2021, astronomy.com/news/2021/02/outer-space-is-a-treasure-chest-of-gemstones.

Starr, Michelle. “Astronomers Have Found a New Type of Planet That’s Absolutely Riddled With Gemstones.” ScienceAlert, 20 Dec. 2018, www.sciencealert.com/hot-super-earths-are-so-riddled-with-rubies-and-sapphires-they-may-shimmer.

University of Warwick. “Winds of Rubies and Sapphires Strike the Sky of Giant Planet.” Exoplanet Exploration: Planets Beyond Our Solar System, 12 Dec. 2016, exoplanets.nasa.gov/news/1397/winds-of-rubies-and-sapphires-strike-the-sky-of-giant-planet.

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