Diamonds: Characteristics
The four Cs, and why hardness matters in industry
What this tab covers The supply and physical characteristics of the commodity. Supply: current production, inventories and stocks, capacity utilisation, geographic and producer concentration, how fast supply responds to price, the project pipeline and capital spending, and logistics and export flows. Material: the physical and chemical properties that set its grade, price and end uses (for example purity and conductivity for metals, API gravity, sulfur and energy content for fuels, moisture, protein and fibre quality for crops).Supply volume characteristics
| Characteristic | Figure | What it means | Source |
|---|---|---|---|
| Current production volume | about 107 Mct natural diamond (2025e), of which about 69 Mct gem quality; synthetic industrial diamond over 15 billion ct | World Mining Data gives 65.7 Mct of gem and 41.5 Mct of industrial natural diamond in 2024. Synthetic diamond is more than 99% of industrial diamond. | USGS MCS 2026, Gemstones and Diamond (Industrial); World Mining Data 2024 |
| Inventory and stock levels | not published; midstream stocks built up after 2023 | Weak jewellery sales since 2023 left cutters and dealers with excess polished stock, so they bought less rough. De Beers produced 21.7 Mct but sold 20.9 Mct in 2025, adding to its own rough stock. | USGS MCS 2026; De Beers results via Engineering News (2026) |
| Capacity utilisation | not published; De Beers produced 21.7 Mct in 2025 against 24.7 Mct in 2024 | De Beers cut 2025 guidance to 20-23 Mct. Many Surat cutting units ran short weeks during the downturn (indicative). Mines are maturing and several of the largest are near the end of open-pit life. | De Beers results via Mining Weekly and Engineering News (2026); USGS MCS 2026 |
| Geographic and producer concentration | Gem: Russia 29.5%, top-3 (Russia, Botswana, Angola) 69.4%, HHI 2,032. Industrial: Russia 43.2%, HHI 2,680 | De Beers (21.7 Mct) and Alrosa are the two dominant miners. India cuts about 9 in 10 of the world's diamonds, a far higher concentration than in mining. | World Mining Data 2024; GJEPC via Reuters (2025) |
| Supply elasticity | low upward, moderate downward: miners can cut output and hold stock, but new mines take a decade or more (indicative) | Few major kimberlite discoveries have been made in recent decades. Producers respond to gluts by cutting output and withholding sales, as De Beers and Alrosa did in 2023-25. | USGS MCS 2026; De Beers (2026) |
| Project pipeline and CapEx | small: underground extensions rather than new mines | De Beers' Venetia Underground (South Africa) and the Jwaneng underground project (Botswana) extend existing mines into the 2040s (indicative). USGS expects natural output to keep declining as mines deplete. | USGS MCS 2026; De Beers announcements (indicative) |
| Logistics and export flows | HS 7102 exports $66.6 billion (2024); India 21.3%, US 18.7%, Hong Kong 18.3% of exports | Rough moves by air from Gaborone, Windhoek and Moscow to Antwerp, Dubai and Mumbai, then to Surat for cutting, and polished back out through Mumbai, Hong Kong, New York and Antwerp. India imported 25.1% of world trade by value. Kimberley Process certificates and G7 bans on Russian stones are the main frictions. | UN Comtrade 2024 (HS 7102); USGS MCS 2026 |
Material characteristics Industrial mineral
A diamond's value depends on the four Cs: carat weight, colour, clarity and cut. Small differences in grade can change price per carat several-fold. For industry, the value lies in hardness and thermal conductivity, the highest of any bulk material, which is why saws, drill bits and heat spreaders use synthetic grit and plates. Distinguishing natural from lab-grown stones now requires spectroscopy.
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Carat weight | 1 carat = 0.2 g; price per carat rises steeply with size | Main driver of value per stone | GIA grading standard |
| Colour | GIA scale D (colourless) to Z (light yellow); fancy colours graded separately | Each grade step changes price materially | GIA grading standard |
| Clarity | GIA scale FL (flawless) to I3 (included), assessed at 10x | Sets value and suitability for jewellery | GIA grading standard |
| Cut | Excellent to Poor for round brilliants; refractive index 2.42 gives fire and brilliance | Well-cut stones sell at a premium | GIA grading standard; CRC Handbook |
| Hardness | 10 on the Mohs scale, about 10,000 HV | Basis of industrial cutting, drilling and polishing uses | Mineralogy references |
| Thermal conductivity | about 2,000 W/m K, roughly five times copper | Heat spreaders and testing to tell diamond from simulants | CRC Handbook (indicative) |
| Type (nitrogen content) | Type Ia (most natural) vs Type IIa (rare natural and most CVD lab-grown) | Screening machines use this to flag lab-grown stones | GIA (indicative) |