The Journey of a Diamond

Carbon at Extreme Depths

Natural diamonds form more than 120 kilometres beneath the surface, where temperatures range from 900 °C to 1,300 °C and pressures soar to 45–60 kilobars. In this hidden realm, carbon atoms that once drifted freely in Earth’s mantle find themselves squeezed so intensely that they reorganise into a rigid crystal structure. This environment exists in regions rich in molten kimberlite and lamproite, the very magmas that will later carry these nascent gems upward.

Crystallisation Under Pressure

Under those immense conditions, each carbon atom bonds in a perfectly repeating tetrahedral lattice. This arrangement creates the diamond’s signature strength so unrivalled that diamond is the hardest known natural substance. Over spans of hundreds of millions to billions of years, the crystal grows, layer by layer, deep in the diamond stability zone of the upper mantle.

The Ascent in Kimberlite and Lamproite Magma

Diamonds reach the surface when deep-source volcanic eruptions force kimberlite or lamproite magma skyward. In these rapid eruptions, magma tears through the mantle’s rock layers, plucking diamond-bearing fragments called xenoliths and enclosing them in vertical “pipes.” As the molten rock cools, it solidifies into kimberlite or lamproite, trapping gem-quality crystals within its heart.

Pipes, Placers, and Mining

Most commercial diamonds are recovered from these vertical kimberlite and lamproite pipes, where they lie embedded in hard volcanic rock. Over time, weathering can free diamonds, depositing them in riverbeds and along coastlines as alluvial gravels. Prospectors follow these placers as clues to the pipe’s original source, often leading to large-scale open-pit or underground operations in Western Australia and beyond.

Rare Origins: Subduction, Impact and Space

While kimberlite pipes produce the vast majority of mined diamonds, rare stones form under other extraordinary conditions. Some grow in subduction zones where oceanic plates dive beneath continental crust, experiencing pockets of extreme heat and pressure. A handful have crystallised at meteor-impact sites or even condensed from carbon-rich material in space, later deposited on Earth’s surface by ancient asteroidal collisions.

Lab-Grown Diamonds: Mimicking Nature

Synthetic diamonds replicate these natural forces in controlled settings using two primary methods. The high-pressure high-temperature (HPHT) technique surrounds a diamond seed with carbon and subjects it to extreme pressure and heat to encourage growth around the core. In chemical vapor deposition (CVD), methane gas decomposes under high heat in a vacuum chamber, allowing pure carbon to layer onto a seed. Though lab-grown diamonds match natural stones in composition, large gem-quality crystals remain costly and specialized.

From Rough Stone to Radiant Jewel

Once mined or grown, each rough diamond arrives at Custom Jewellery Designs where it is carefully sorted for clarity, cut potential and colour. Our expert craftsmen then transform these raw crystals into custom creations, blending technical precision with the imaginative flair that defines our brand. Every finished piece carries both the ancient saga of its formation and the personal story you choose to tell.

Diamonds connect us to the Earth’s deep history and to moments of human creativity and celebration. As you design your next bespoke piece with us in Hillarys, remember the extraordinary journey each diamond has taken from carbon under unimaginable pressure to the centerpiece of your personal story.