Kimberlite Pipe Mining
Open-pit and underground mining of the original volcanic pipes the primary source. Legendary mines like Jwaneng (Botswana), Cullinan (South Africa) and Diavik (Canada) work kimberlite deposits.
Before a diamond ever sparkles in a ring, it spends billions of years as a rough crystal deep inside the earth. This complete guide explains how rough diamonds form, how they are mined, sorted, valued and transformed into the polished stones we cherish.
A rough diamond is a diamond exactly as nature made it uncut, unpolished, and untouched by human hands. Rough diamonds form between 150 and 250 kilometres beneath the earth's surface, where extreme pressure and temperatures around 1,100°C bond pure carbon atoms into the hardest natural material known.
These crystals are then carried to the surface in rare, violent volcanic eruptions through pipes of a rock called kimberlite nature's elevator for diamonds. Most rough diamonds are older than life on land: many formed one to three and a half billion years ago.
In its natural state, a rough diamond often looks like frosted glass or a translucent pebble. Its true fire is hidden revealed only through the skill of the cutter.
Diamond crystallises in the cubic system, so most rough stones grow in a handful of recognisable natural forms. The shape of the rough decides what the polished diamond can become.
On average, around 250 tonnes of ore must be processed to recover a single one-carat gem-quality rough diamond. Three methods bring rough to the surface.
Open-pit and underground mining of the original volcanic pipes the primary source. Legendary mines like Jwaneng (Botswana), Cullinan (South Africa) and Diavik (Canada) work kimberlite deposits.
Over millions of years, rivers eroded kimberlite and carried diamonds downstream. Alluvial rough recovered from riverbeds and gravel is often naturally rounded and of high average quality, as weaker stones broke apart on the journey.
Off the coast of Namibia, specialised vessels recover diamonds from the seabed, where rivers deposited them into the ocean. Marine rough has among the highest gem-quality percentages in the world.
Rough diamonds are first divided into gem quality, near-gem and industrial categories. Gem rough is then valued on five factors that experienced diamantaires read at a glance.
| Factor | What the Expert Looks For |
|---|---|
| Size (Weight) | Larger rough is exponentially rarer. Price per carat rises steeply with size, because large clean crystals are among nature's rarest creations. |
| Shape (Model) | A well-formed octahedron yields the most polished weight. Distorted or flat rough loses more material in cutting, lowering its value per carat. |
| Colour | Rough is graded from colourless toward brown and yellow tints and, rarely, fancy colours like pink or blue that multiply value dramatically. |
| Purity (Clarity) | Internal inclusions, cracks and "gletzes" visible inside the rough determine how clean the polished stones can be and where the cutter must divide the crystal. |
| Expected Yield | The ultimate question: what polished diamonds can this rough become? A skilled buyer values rough by picturing the finished stones inside it. |
This is where generational expertise matters most reading a rough crystal correctly is the foundation of every fine polished diamond we offer. Learn how those polished stones are graded in our Diamond Education & Guide.
A rough diamond typically loses 50–60% of its weight to become a polished gem. Every step is irreversible which is why planning is everything.
Since 2003, the Kimberley Process Certification Scheme (KPCS) has governed the international trade in rough diamonds. Rough may only cross borders in tamper-proof containers with a government-issued Kimberley certificate, ensuring diamonds do not finance conflict.
Dubai is a Kimberley Process participant, and all rough diamond trade in the UAE flows through certified channels under DMCC oversight one of the world's most regulated diamond hubs.
As a DMCC-registered diamantaire in Almas Tower, Ratan Sajan sources exclusively through Kimberley-compliant channels, so every polished diamond we offer begins with an ethical rough.
Discovered in South Africa in 1905 the largest gem-quality rough ever found. It was cleaved into nine major stones, including the Great Star of Africa in the British Crown Jewels.
Recovered in Botswana in 2019, the second-largest rough diamond in history a ball of crystal so unusual it was acquired by Louis Vuitton before cutting.
"Our Light" in Tswana — found in Botswana in 2015 and later cut into Graff's flawless 302-carat Lesedi La Rona, the largest square emerald cut in the world.
Most rough diamonds look like translucent, frosted pebbles or glassy crystals with a slightly greasy lustre. The most recognisable form is the octahedron two four-sided pyramids joined at the base. Their brilliance only appears after cutting and polishing.
Per carat, yes but the rough price already reflects the polished stones it can yield, minus cutting cost and risk. Since 50–60% of the weight is lost in cutting, a rough diamond and its resulting polished diamond represent similar underlying value.
Yes raw diamond jewellery is a growing niche prized for its organic, natural look. However, rough set in jewellery cannot be certified with standard 4C grades, so buy only from a trusted diamantaire who can verify origin and authenticity.
Diamond is the hardest natural material (10 on the Mohs scale), has a distinctive greasy adamantine lustre, is not water-wettable, and conducts heat exceptionally well which is how thermal diamond testers work. Definitive identification should always be done by a gemological laboratory.
Only around 20–30% of mined rough is gem quality suitable for jewellery. The remainder is near-gem or industrial grade, used for cutting tools, drilling and abrasives.
Dubai has grown into one of the world's top rough diamond trading hubs. Through the Dubai Diamond Exchange in Almas Tower where Ratan Sajan is based — billions of dollars of Kimberley-certified rough are traded annually between Africa, India and global markets.
Based in Almas Tower home of the Dubai Diamond Exchange Ratan Sajan offers certified polished diamonds with expertise that begins at the rough.
View Certified Diamond Rings Diamond Education Guide