Small South African town that produced the world’s largest diamond uses X-ray transmissions and AI to recover valuable stones
Cullinan, roughly 45km to the north-east of Pretoria, has transformed from a colonial outpost into an innovative diamond-mining town, using X-ray transmissions and AI to recover valuable diamonds.
It was here where the Cullinan Diamond, the world’s largest diamond, was discovered. It weighed 3,106.75 carats and was cut into nine diamonds, two of which became part of the British Crown Jewels.
The town was founded in 1902 following the discovery of the Cullinan kimberlite, a 1.2-billion-year-old diamondiferous pipe that became renowned for producing large, high-quality diamonds.
Kimberlite is a dark-coloured, rare, ultramafic igneous rock that is known to be the primary source of diamonds. The town was named after Sir Thomas Cullinan, who was the owner of its first mine.
Open-pit mining at the Premier Mine began in 1903. Two years after the mining operation commenced, Frederick George Stanley Wells discovered the Cullinan Diamond.
Wells was the surface manager of the Premier Diamond Mining Company. Following the diamond’s discovery, it was bought by the Transvaal government and presented to King Edward VII.
Today, the Cullinan diamond remains the largest gem-quality rough diamond ever found. However, the town underwent significant changes.
While it still features a Victorian-era aesthetic, the industrial mining side evolved into a “smart mine,” which is operated by Petra Diamonds.
Petra Diamonds shifted the approach from traditional open-pit mining to an underground mining operation that reaches into the earth by more than a kilometre.
The change in approach came as a result of the easier-to-find diamonds near the surface depleting as the mine aged.
In 2011, Petra Diamonds initiated the first phase of a C-Cut expansion at the Cullinan mine, followed by undercutting, which began in 2015.
The Petra Diamond Mine in Cullinan reached steady-state production in 2019, and the expansion extended the mine’s life until at least 2030.
Precision diamond extraction
Through the transition to underground mining, Cullinan evolved into a hub for specialised engineering and digital mining technology.
Petra Diamonds uses X-ray Transmission (XRT) technology to precisely extract diamonds from the Cullinan mine.
XRT uses sensors that can identify the atomic signature of carbon. As kimberlite ore travels along Petra Diamonds’ high-speed conveyor belts, the XRT sensors effectively see into the material.
When the sensors detect a diamond, a blast of compressed air separates the rock from the rest of the material, with millisecond timing precision.
As a result, Petra Diamonds isn’t mining for quantity. The XRT extraction technology enables it to target larger, Type II diamonds.
Type II diamonds are often more brittle, and the XRT system can separate them from the kimberlite before they go through secondary crushing stages.
The Petra Diamonds Mine in Cullinan is also supported by a resilient digital ecosystem. It uses a technique called Block Caving, which involves undercutting entire blocks of ore.
The undercutting allows for a self-sustaining collapse of the mine into automated draw points where the ore can be extracted.
Petra Diamonds monitors this process using a virtual replica of the mine and real-time sensor data to predict ore flow and prevent bottlenecks.
The mining operation also relies heavily on Internet of Things technology, with every piece of machinery fitted with sensors that feed data into AI models.
The models provide predictive maintenance alerts, ensuring that the mine operates with minimal downtime.
Diamond mining in Cullinan, Gauteng
The town of Cullinan in Gauteng
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