Diamond exploration is the search for kimberlite and lamproite pipes that carry diamonds, and for the river, beach and marine gravels where eroded diamonds have been concentrated. Because diamonds are so rare in their host rock, explorers rarely look for the diamonds themselves at first. They look for the heavy minerals that travel with them, trace those minerals back to a source, and only then drill and bulk-sample.

Try it: Diamond bulk-sample grade and value per tonne →

The economics are unforgiving. The USGS gemstones summary notes that most diamond ore bodies contain from less than 1 carat to about 6 carats per tonne of ore, and that the natural diamond market has been in a downturn since early 2023, hit by inventory build-up and cheaper synthetic stones. A diamond project has to clear both a geological bar and a market one. Our guide to prospecting and deposit types sets out the same target-ranking logic for gold.

“Diamond is usually far below 1.4 ppm of the kimberlite that carries it.”

Where diamonds come from: kimberlites and cratons

Diamonds form deep in the mantle and reach the surface in rare, fast-rising volcanic rocks, mainly kimberlite. The USGS notes that the major diamond reserves are in southern Africa, Australia, Canada and Russia, and that natural diamond deposits have been discovered in more than 35 countries. Most productive pipes sit on old, thick continental cratons, which is why diamond exploration concentrates on Archean terrains such as the Kaapvaal Craton in southern Africa and the Slave Province in Canada.

Kimberlite is a distinctive rock. Geological Survey of Canada scientists McClenaghan and Kjarsgaard describe it as a mineralogically and geochemically distinct point source that leaves discrete dispersal trains in glacial sediments and dispersion fans in stream sediments. Diamond itself is usually far below 1.4 ppm of the rock, so explorers rely on a subset of “diamond indicator” minerals that formed alongside it.

The indicator minerals

Kimberlite exploration methods, step by step

Kimberlite exploration in practice follows the indicator minerals upstream or up-ice. The Canadian survey scientists note that kimberlite indicator minerals generally survive long-distance glacial transport, and that the 0.25 to 2.0 mm fraction of heavy-mineral concentrates from till and stream sediments is typically used, with the finer 0.25 to 0.50 mm fraction often giving the best results.

1. Pick the terrain. Old cratons, known kimberlite fields and structural corridors that could have channelled magma.
2. Regional sampling. Stream sediments in unglaciated country; till in glaciated country. Pick indicator grains from heavy-mineral concentrates.
3. Mineral chemistry. Analyse garnets, chromites and ilmenites to rank which trains carry diamond-favourable compositions.
4. Trace the train. Tighter sampling narrows the source. In glaciated terrain, dispersal runs from a few tens of metres to tens of kilometres down-ice.
5. Geophysics over the head of the train. Magnetics, EM and gravity look for a small, roughly circular body; kimberlite responses vary, so no single signature is diagnostic.
6. Drill the anomaly. Confirm kimberlite, then take mini-bulk and bulk samples for diamond content.

This combination has a track record. In Canada, indicator-mineral methods were first used for kimberlite in the early 1960s, and with geophysics they led to the discovery of kimberlite fields in northern Ontario in the 1980s and the highly diamondiferous Lac de Gras field in the Northwest Territories in the early 1990s, according to the same Geological Survey of Canada review.

Olivine deserves a mention. The review notes that kimberlitic olivine easily survives glacial transport, unlike in arid and tropical terrains, and is visually distinct from olivine from other rocks, so it should be used alongside the more common indicators in glaciated ground. In nonglaciated terrains, chemical and physical breakdown changes the relative abundance of indicator species, which is why tropical programmes lean on the most resistant grains.

Geophysics for kimberlite pipes

Once indicator trains point to an area, geophysics looks for the pipe itself. Kimberlites are small targets compared with most ore bodies, and their physical properties vary. Some pipes are more magnetic than the rocks around them and some less; weathered or clay-rich pipes can show as electrical conductors; others show as subtle gravity lows. Explorers therefore fly magnetics and EM over the head of the train, rank the small, roughly circular anomalies that sit where the indicator evidence points, and test the best with ground surveys before drilling. An anomaly with no indicator support is a weak target, however neat it looks on a map.

Till geochemistry and pathfinders

Till geochemistry is cheaper and faster than picking indicator grains, so it has become more popular in diamond exploration. McClenaghan and Kjarsgaard list kimberlite pathfinder elements including magnesium, nickel, chromium, cobalt, niobium, tantalum, the rare earths, potassium, rubidium, strontium and barium, with the best choice depending on how the kimberlite differs from the surrounding rock.

Grade, value and bulk sampling

Diamond grade is reported in carats per hundred tonnes (cpht) or carats per tonne. Value is reported in US dollars per carat, and it varies enormously with stone size, colour and quality. That is why diamond exploration companies take bulk samples of hundreds or thousands of tonnes: small samples recover too few stones to estimate either number reliably, and the largest, most valuable stones are the rarest.

Revenue per tonne is simply grade times value. A pipe at 50 cpht with stones worth US$300 per carat yields about US$150 per tonne of ore. The same grade at US$60 per carat yields only US$30. The calculator below shows how quickly that changes the picture.

Diamond exploration companies and the market

Diamond exploration companies are a small group today. Natural Resources Canada’s April 2026 bulletin puts Canadian diamond exploration spending at only C$6.8 million in 2025 (preliminary), less than 1% of the national total. S&P Global’s global survey also listed diamonds among the commodities whose budgets fell in 2025.

The USGS explains why. The downturn that began in early 2023 has especially affected stones of one carat or less. Lower jewellery sales led to midstream inventory build-up, lower rough prices and pressure on mines. Sanctions by the United States, the European Union and the G7 on Russian rough and polished diamonds remained in force in 2025. The USGS also notes that the world’s largest diamond mines are past their peak and several are expected to close, so global natural output is expected to keep declining. For a diamond explorer, that is a mixed signal: weaker prices now, but fewer new mines to replace the old ones.

Alluvial diamonds in South Africa and along the West Coast

Not every diamond deposit is a pipe. Erosion of kimberlites over tens of millions of years released diamonds into rivers, which carried them to the coast. Because diamonds are hard and dense, they survive the journey and collect in gravel traps along the way and at the coast.

In South Africa, the Orange-Vaal river system is the main secondary source for alluvial diamond deposits in the Northern Cape and along the West Coast of Namaqualand, according to a paper by P.G. Gresse in the Journal of the South African Institute of Mining and Metallurgy. Gresse notes that the higher-order sources include kimberlite pipes in the rivers’ catchments, and that mining focus had shifted from the upper catchment around Barkly West and Christiana, and the river mouth near Alexander Bay and Oranjemund, to the middle Orange between Douglas and Prieska. There, exploration revealed remnants of an older meandering river system buried under sand and calcrete.

How alluvial diamond exploration works

• Map the old river courses. Terraces, abandoned meanders and buried channels hold the gravels. Satellite imagery and elevation data are the natural first tool.
• Find the bedrock traps. Potholes, gullies and the inside of bends concentrate diamonds at the base of the gravel.
• Measure gravel volume. Pitting, trenching and large-diameter drilling estimate thickness and extent; GPR or resistivity can help in suitable ground.
• Bulk-sample through a plant. Dense-media separation and X-ray recovery process large volumes to estimate grade in carats per hundred cubic metres or per hundred tonnes.

South Africa produced about 2.1 million gem carats in 2025 and about 3 million carats of natural industrial diamond, according to the USGS. Namibia, on the far side of the Orange River mouth from Alexander Bay, produced about 2.3 million gem carats. Licensing in South Africa is covered in our guide to mining and prospecting rights in South Africa.

Tanzania diamonds and East African kimberlites

Tanzania has one of the densest kimberlite records in Africa. The Tanzania High Commission’s minerals outlook states that over 300 kimberlites are known in the country, about 20% of them diamondiferous. Diamond deposits are mainly in Shinyanga Region, at Mwadui, Mabuki and Maganzo, and areas in Tabora and Singida are flagged for further exploration. The USGS estimates Tanzanian gem-diamond production at about 320,000 carats in 2025.

Those numbers set the odds for Tanzania diamonds: roughly one known kimberlite in five carries diamonds at all, and a smaller share will be economic. That is typical of kimberlite fields. The practical sequence is the same as elsewhere: stream-sediment indicators in the Shinyanga and Tabora drainages, mineral chemistry to rank them, geophysics over the heads of the trains, then drilling and bulk sampling. Tanzania’s licence rules are set out in our Tanzania mining cadastre guide.

Canada, Botswana and the other big producers

Canada, Botswana and Angola each produced about 13 million gem carats in 2025, and Russia about 21 million, according to the USGS. Canada’s industry grew from exploration that began with indicator minerals in the 1960s and led to the Lac de Gras discoveries in the early 1990s. In glaciated terrain like the Slave Province, the dispersal train is the key tool: glacial erosion spread kimberlite debris down-ice, and modern streams carried grains up to several tens to hundreds of kilometres from source, the Geological Survey of Canada review notes.

In unglaciated southern and central Africa, streams do the dispersing instead of ice, so stream-sediment sampling replaces till sampling and dispersal fans follow the drainage. The same Canadian review notes that kimberlite leaves dispersion fans in stream sediments as well as trains in till, so the method carries over; only the sampling medium changes.

For diamond exploration companies working in Canada today, the lesson of Lac de Gras is about patience and sampling density. Many government agencies have since run regional diamond exploration surveys in Canada, according to the review, so many areas already have public indicator data. A new programme should start by compiling it, then fill gaps and follow the most diamond-favourable chemistry, rather than resampling ground that has already been tested.

How to judge a diamond project

Whether you hold a diamond licence, want to partner with diamond exploration companies or are reviewing a project for sale, the same questions sort strong projects from weak ones.

1. Is kimberlite confirmed? A geophysical anomaly or an indicator train is not a pipe. Ask for drill core or outcrop descriptions.
2. What do the indicators say? Ask for mineral chemistry, especially the share of G10 garnets and diamond-inclusion-field chromites, not just grain counts.
3. How big was the bulk sample? Tens of tonnes can confirm diamonds are present. Grade and value estimates need much larger samples.
4. What was the bottom cut-off? Grade depends on the smallest stone size recovered. Compare projects on the same cut-off.
5. Who valued the stones? An independent valuation of a parcel large enough to represent the deposit is essential.
6. For alluvials, how much gravel is there? Grade per cubic metre means little without a gravel volume and a bedrock profile.
7. Is the title clean? Check the licence in the national cadastre and confirm that Kimberley Process export rules can be met.

Common mistakes in diamond exploration

• Counting grains without chemistry, which treats barren and diamond-favourable kimberlite as the same.
• Sampling the wrong fraction, when the 0.25 to 0.50 mm fraction often gives the best results in till.
• Ignoring ice-flow history, so the train is traced in the wrong direction in glaciated terrain.
• Drilling geophysics alone, without indicator support at the anomaly.
• Reporting carats without value, which hides the number that decides whether a pipe pays.

Diamond exploration terms in plain English

Kimberlite

A rare volcanic rock from deep in the mantle and the main primary host of diamonds. It usually forms small pipes.

Indicator minerals

Heavy, resistant grains such as Cr-pyrope garnet, chromite, Mg-ilmenite and Cr-diopside that travel with kimberlite and point back to it.

G10 garnet

A low-calcium, high-chromium pyrope garnet from harzburgite or dunite, the mantle rocks most closely linked to diamond.

Dispersal train

The trail of kimberlite debris spread down-ice by glaciers or downstream by rivers from a pipe.

cpht

Carats per hundred tonnes, the usual unit of diamond grade. 100 cpht equals 1 carat per tonne.

Bottom cut-off

The smallest stone size a processing plant recovers. A lower cut-off recovers more carats but usually of lower average value.

Bulk sample

A large sample, often hundreds to thousands of tonnes, processed to estimate grade and to recover enough stones for valuation.

Dense-media separation (DMS)

A processing step that concentrates heavy minerals, including diamonds, from crushed rock or gravel.

How satellite screening fits diamond exploration

Diamonds are on our published list of detectable materials. Satellites can’t see a diamond, but they can map the settings that matter: small circular features and vegetation or soil anomalies that may mark pipes, structural corridors on cratons, and the terraces, meanders and palaeochannels that hold alluvial gravels. Our satellite-based mineral detection analyses multispectral and hyperspectral data over your licence to flag target zones, alteration, faults and fractures, and deposit-associated patterns before sampling crews go in.

• Input: coordinates, KML/KMZ or a polygon, plus country and target mineral.
• Output: high-potential zones, prospectivity heatmaps, estimated location and depth ranges, geological interpretation and seasonal anomaly validation, as PDF and GIS files.
• Time and cost: 5–20 business days; early-exploration timelines cut from months to days and costs lowered by up to 80–85%.
• Premium+: TargetMax™ drilling-angle recommendations and interactive 3D subsurface models.
• ⚠ Limits: a satellite target is not a pipe or a grade. Indicator sampling, drilling and bulk sampling decide.

We have scanned 100,000+ hectares for 20+ mineral types across 25+ countries. See a sample of satellite-driven 3D mineral prospectivity mapping, or ask for pricing through our mining query form. For the wider exploration process, see our mineral exploration guide.

Frequently asked questions

Reviewed September 2026 against the USGS Mineral Commodity Summaries 2026 chapters on gemstones and industrial diamond, McClenaghan and Kjarsgaard’s Geological Survey of Canada review of indicator-mineral methods for kimberlite, Gresse’s paper on alluvial diamonds of the middle Orange River in the SAIMM Journal, the Tanzania High Commission’s minerals outlook, Natural Resources Canada’s April 2026 exploration bulletin and the Kimberley Process’s own description of the certification scheme.

Production and spending figures are estimates that the USGS and NRCan revise each year; check the latest editions. Nothing here is investment advice and we do not recommend any company. Satellite targets are exploration targets, not mineral resources, and need indicator sampling, drilling and bulk sampling to confirm.