When you hear the phrase “10 amazing things,” you probably think of glitter and glamour. But diamonds are far more than just dazzling jewelry; they are geological time capsules that hold some of the most astonishing secrets of our planet. From hidden oceans to extraterrestrial carbon, these ten wonders reveal what lies deep beneath the surface.
10 Amazing Things Inside Diamonds
10 Ringwoodite
Scientists have long suspected that a massive ocean exists deep within Earth’s mantle, hidden inside a green mineral known as ringwoodite. This mineral only forms in the transition zone—a narrow band roughly 515 kilometers (320 miles) beneath the surface, sandwiched between the upper and lower mantle.
Ringwoodite cannot survive at the surface because the crushing pressures required for its stability vanish once it’s brought up. While researchers have occasionally captured it in the lab, it swiftly transforms into another phase once the pressure drops. Geochemist Graham Pearson, however, succeeded in preserving ringwoodite in its natural state.
The breakthrough came when a diamond from a Juína, Brazil mine was examined. Pearson and his team hypothesized that a seismic event ferried the mineral to the surface. Interestingly, the discovery was accidental—Pearson was originally dating the diamond when he noticed the unexpected ringwoodite inclusion.
9 Calcium Silicate Perovskite
Paradoxically, silicate perovskite is the most abundant mineral in the Earth, yet it remains one of the rarest to encounter directly. Roughly 38 % of Earth’s volume is believed to consist of this mineral, but because it resides deep within the mantle, no surface samples have ever been collected.
The tide turned when scientists identified a stable specimen lodged inside a diamond excavated just a kilometer (0.6 mi) beneath the Cullinan Mine in South Africa. The mineral in question is calcium silicate perovskite (CaSiO₃), thought to be the fourth‑most common mineral on the planet.
The host diamond is extraordinary, having formed roughly 700 km (435 mi) below the crust under pressures 240,000 times greater than at sea level. Researchers believe the perovskite became entrapped as the diamond crystallized under these extreme conditions.
8 Ice
Earlier speculation about a deep‑Earth ocean suggested that seawater could be dragged down as the crust subducts into the mantle. While the exact size and longevity of this hidden ocean remain uncertain, recent findings have bolstered the hypothesis.
In March 2018, researchers reported the capture of ice crystals within diamonds that formed deep inside the mantle. The ice, termed ice‑VII, is thought to originate from water that migrated downward with the sinking crust, solidifying under extreme pressure.
Ice‑VII only crystallizes between 610 km and 800 km (379 mi–497 mi) beneath the surface, where pressures exceed 24 gigapascals. To date, three such samples have been documented—two from South African mines and one from a Chinese mine.
7 Liquid Metals
Some of the planet’s largest diamonds were forged at depths ranging from 322 km to 805 km (200 mi–500 mi) within the mantle. These colossal gems often encapsulate metallic impurities that offer a glimpse into the mantle’s composition.
Analysis of 53 such diamonds revealed abundant iron and nickel, alongside trace amounts of methane, hydrogen, and garnet. Curiously, oxygen—a presumed major component—was absent, challenging long‑standing assumptions about mantle chemistry.
6 Harzburgitic Inclusions
Harzburgitic inclusions belong to a subset of peridotite rocks, the most common rock type within Earth’s mantle. Their prevalence makes them useful markers for dating diamonds.
A team at Vrije Universiteit Amsterdam examined 26 diamonds containing these inclusions. Nine of the specimens dated back roughly three billion years, a period marked by continental breakup and intense deep‑earth heating.
Remarkably, ten diamonds were determined to be just 1.1 billion years old—a surprising find, as most diamonds are significantly older. Researchers attribute this youthful age to a massive volcanic eruption in present‑day Zimbabwe, which likely supplied the necessary heat to forge these comparatively recent gems.
5 Boron Molecule
While carat weight is a primary driver of a diamond’s price, the stone’s color—often dictated by trace minerals—plays a crucial role as well. Blue diamonds rank as the second rarest colored variety, trailing only the ultra‑scarce red diamonds.
In 2016, the 24.18‑carat Cullinan Dream, a striking blue diamond, fetched over $23 million at auction. Its vivid hue stems from boron, a rare element in the deep Earth. Most boron resides in the oceanic crust, making its presence at mantle depths a geological curiosity.
Scientists propose that dense tectonic plates, when thrust beneath lighter plates, transport boron (along with methane, hydrogen, and seawater) deep into the mantle, where it becomes incorporated into growing diamonds.
4 Kyanite
Occasionally, diamonds emerge with other gemstones encapsulated within them—rubies, for instance, or the lesser‑known kyanite. While kyanite comes in a rainbow of colors, its blue variety commands the highest market value, even though the pure white form is technically rarer.
Unscrupulous sellers sometimes pass off blue kyanite as the more expensive blue sapphire, underscoring the importance of informed appraisal.
3 Mutated Carbon Atoms
Carbon is famous for existing as diamond, graphite, or buckminsterfullerene, but scientists have identified two exotic forms that are even harder than diamond. These super‑hard crystals were predicted theoretically long before they were observed.
The breakthrough came from the Havero meteorite—a ureilite that fell in Finland in 1971. This meteorite type typically harbors both graphite and diamond.
Researchers believe that as the meteorite barreled through Earth’s atmosphere, intense heating transformed some graphite into a mutated carbon structure, yielding the ultra‑hard crystals.
Because the crystals are minuscule, direct hardness measurements proved impossible. However, their resistance to polishing with diamond paste indicated they surpass diamond in hardness.
2 Carbon‑12
In 1983, a team from Curtin University examined 22 diamonds nestled within zircon crystals from the Jack Hills region of Western Australia. Chemical analysis revealed these diamonds were composed almost entirely of carbon‑12, a light isotope typically associated with biological activity.
Radiometric dating placed the diamonds at 4.2 billion years old, while the surrounding zircons formed 4.4 billion years ago. This predates the previously accepted emergence of single‑celled life by roughly 700 million years, suggesting life may have arisen during the Hadean eon.
Given the extreme conditions of early Earth—scorching temperatures, a magma‑filled ocean—some scientists argue the carbon‑12 may have arrived via extraterrestrial delivery, such as meteorites, rather than indigenous biological processes.
1 Ferropericlase
Finding diamonds that formed deep within the mantle is a rarity, yet researchers at the Gemological Institute of America (GIA) have identified a handful containing ferropericlase—a mineral native to the lower mantle.
These ferropericlase‑bearing diamonds are instantly recognizable by their iridescent sheen, which shifts color with the angle of observation, reminiscent of light dancing through a soap bubble. The phenomenon may stem from fluid inclusions or magnesioferrite within the crystal lattice.
Not every ferropericlase inclusion produces a rainbow effect; some diamonds appear as transparent brown. Moreover, the mere presence of ferropericlase does not conclusively prove mantle origin, as such inclusions can also form in silica‑deficient environments nearer the surface.