Only about 20% of mined diamonds are of gem quality, meaning they meet the necessary standards for use in jewellery. The remaining 80% fall into the industrial-grade category, used in various commercial and technological applications. Let’s explore this in more detail:
Breakdown of Diamond Quality
Gem-Quality Diamonds (≈20%)
These diamonds are characterised by high clarity, colour, and cut quality, making them desirable for jewellery.
They undergo cutting and polishing to enhance their brilliance before being set in rings, necklaces, earrings, and other fine jewellery.
Their value depends on the 4 Cs (Carat, Cut, Colour, Clarity) and whether they are natural or treated.
Industrial-Grade Diamonds (≈80%)
These diamonds are lower in clarity, may have visible inclusions, and often exhibit yellow, brown, or grey colours that make them unsuitable for jewellery.
They are used in industries due to their hardness and durability, which are essential for cutting, drilling, grinding, and polishing applications.
Common uses include:
Diamond-tipped drill bits and saw blades for construction and mining.
Abrasive powders for polishing and grinding metals.
High-tech applications, such as semiconductors and heat conductors in electronics.
Why the Low Percentage of Gem-Quality Diamonds?
Several factors contribute to why only a small fraction of mined diamonds qualify as gem-grade:
Formation Conditions: Natural diamonds form under extreme pressure and temperature deep within the Earth’s mantle. Impurities or irregular growth can affect their clarity, colour, or shape.
Inclusions and Blemishes: Many diamonds contain internal inclusions (tiny fractures or foreign minerals) and external blemishes, making them less suitable for jewellery.
Colour and Transparency: Gem-quality diamonds are typically colourless to light yellow (D-Z on the GIA colour scale). Many mined diamonds have a strong brown or grey tint, reducing their desirability.
Cutting Yield: Some rough diamonds, even if of good quality, may be inefficiently shaped for cutting into marketable gemstones.
Impact on the Diamond Market
Rarity Drives Value: Since high-quality diamonds are less common, they retain their value better than industrial-grade diamonds.
Lab-Grown Diamonds: The gap in supply between industrial and gem-quality diamonds has led to advancements in lab-grown diamonds, which can be produced with high clarity and controlled quality.
Recycling & Recutting: Some lower-quality diamonds can be recut or treated (e.g., laser drilling, fracture filling) to enhance their appearance, but these diamonds are usually less valuable than untreated stones.
The fact that only 1 in 5 mined diamonds meets gem-quality standards highlights the rarity and value of fine diamonds. This also influences pricing, sourcing strategies, and market trends, as both natural and lab-grown diamonds compete in the luxury and industrial sectors.