Have you ever wondered what kind of rigorous transformation a tiny diamond undergoes before it appears before you? Diamonds do not sparkle naturally; the journey from raw ore to brilliant gemstone involves processing stages that subtly define the stone’s ultimate value. Diamonds circulating in the global market primarily originate from four types of deposits: kimberlite, lamproite, alluvial deposits, and marine diamonds. However, the different types of kimberlite, from the primary kimberlite buried deep in the mantle to alluvial placer deposits eroded by rivers for thousands of years, directly determine the processing methods, recovery rates, and diamond quality. This article provides a systematic overview of these 4 major diamond ore types and reveals the complete processing journey, step by step—from mining and crushing/screening to sorting.
4 types of diamond ore processing: primary kimberlite, alluvial, submarine deposits, and lamproite, each with its own processing focus. For instance, kimberlite processing emphasizes crushing and dense-medium separation; lamproite processing utilizes multi-stage screening combined with fine-particle recovery; alluvial deposits focus on washing to remove clay and jigging for enrichment; and marine deposits rely on specialized mining vessels and gravity-based stratification.
Where Do Diamonds Come From? An Overview of 4 Major Diamond Deposit Types
Primary Deposits vs. Secondary Deposits:
Primary deposits: These refer to deposits where diamonds remain embedded in the host rock in which they were formed; kimberlite and lamproite are the only two major types of primary host rocks. Such deposits typically take the form of volcanic pipes that extend deep into the ancient crust.
Secondary deposits: These are formed when eroded diamond crystals are transported and concentrated to create alluvial placer deposits. Some diamonds are carried by rivers into the sea and accumulate on the continental shelf, forming marine deposits.
Quick Comparison of 4 Diamond Ore Types:
| Type | Ore Body Form | Mining Method | Typical Location | Quality Characteristics |
|---|---|---|---|---|
| Kimberlite (Primary) | Volcanic pipe | Underground blasting | Botswana, South Africa | Complete crystals, high gem-grade proportion |
| Lamproite (Primary) | Volcanic pipe, smaller scale | Open-pit mining, underground mining | Australia | Produces more fancy colored diamonds; pink diamonds are precious |
| Alluvial Deposit (Secondary) | Riverbed sediment | Riverbed panning, mechanical screening | Sierra Leone, DR Congo, Angola | Smooth surface but irregular shape |
| Marine Deposit (Secondary) | Subsea gravel layer | Deep-sea suction dredging vessel | Offshore Namibia | Small particles, pure quality |
4 Major Types of Diamond Ore and Their Processing Characteristics
1. Kimberlite Diamond
Geological Origin: Formed deep within the mantle; diamond-bearing magma rises to the surface and cools, creating a pipe-like ore body. Major deposits are found in regions such as South Africa and Botswana.
Processing Method: The Kimberlite diamond ore consists of large, hard chunks; multi-stage crushing is required to fully liberate the diamond crystals, followed by recovery using heavy-medium separation and X-ray sorting.
2. Lamproite
Geological Origin: Formed in volcanic conduits rich in potassium and magnesium; while its genesis is similar to that of kimberlite, its mineral composition differs significantly, and it is extremely rare globally.
Processing Method: Processing focuses on the recovery of fine-grained material, utilizing multi-stage screening combined with X-ray sorting—a process tailored to the specific characteristics of the ore, which contains a high proportion of small diamonds.
3. Alluvial Deposits
Geological Origin: Primary mineral deposits were formed by the erosion, transportation, and deposition of rivers over millions of years, eventually settling and enriching together with sand and gravel in the slow-flowing bends of rivers.
Processing Method: Rotary scrubbers and high-frequency vibrating screens are used to remove clay impurities in alluvial diamonds, followed by roughing and cleaning stages utilizing jigs and dense-medium cyclones to separate materials based on density differences.
4. Coastal/Marine Placer Deposits
Geological Origin: Distributed along the coastline; formed by ancient rivers depositing sediment into the sea. Reserves are particularly abundant along Namibia’s coast.
Processing Method: Large-scale mining vessels use deep-sea grabs or suction pipes to extract ore-bearing gravel from the seabed. Washing, screening, and separation are performed on board, and tailings are discharged back into the sea after treatment.
From Ore to Diamond: Core Processing Steps
Stage 1: Crushing
A jaw crusher handles the initial coarse crushing, rapidly breaking down large blocks of ore and rock; a cone crusher then takes over for fine crushing, progressively reducing the material to the appropriate size. Multi-crushing must be strictly controlled to ensure the diamonds are cleanly liberated from the surrounding rock while preventing brittle crystals from fracturing or sustaining damage due to impact, thereby preparing a uniform feed for subsequent processes.
Stage 2: Washing and Screening
The crushed ore enters a high-intensity trommel scrubber, where high-pressure water jets remove clay and surface impurities, followed by screening to remove coarse gravel. Subsequently, high-frequency screens are used for precise classification to ensure the feedstock for downstream processing is uniform and meets specifications.
Stage 3: Separation Stage
(1) Dense Medium Separation(DMS):
The mineral feed enters a tank containing a ferrosilicon suspension; diamonds, with a density of approximately 3.52 g/cm³, sink to the bottom, while lighter minerals float and are separated out. This step reduces the volume of material requiring further processing and significantly lowers the load on subsequent sorting stages; it is the primary method for the beneficiation of medium- to fine-grained ores.
(2) Jigging Separation:
For feed materials with a wide size range or high clay content, a jig utilizes pulsating water flow to stratify light and heavy minerals based on density, allowing diamonds to sink to the bottom of the bed for collection. This jig separation method employs simple equipment and consumes relatively little energy, making it particularly suitable for recovering coarser diamond crystals. Furthermore, jigging can be combined with dense medium separation to form a complementary processing circuit.
Stage 4: Intelligent X-ray Sorting
Concentrated ore travels along a conveyor belt through an X-ray beam; diamonds are stimulated to emit characteristic fluorescence, which is detected by sensors that trigger precise ejection via air-blast valves. The system can identify particles with a diameter of 0.1 to 50 mm and is unaffected by surface contaminants. It is the key process with the highest sorting accuracy and the most outstanding recycling efficiency in the entire process.
Stage 5: Magnetic Purification and Tailings Recovery
High-intensity magnetic separators remove magnetic impurities from the ore, ensuring the diamonds meet international trading standards. Following dewatering, the tailings can be used to backfill mined-out areas or manufacture construction materials, thereby enabling resource recycling.
Conclusion
Kimberlite diamond deposits require crushing; alluvial deposits need scrubbing; lamproite ores rely on precision screening; and deep-sea diamonds depend on seabed extraction using specialized vessels. Yet, despite their vastly different geological origins, these four types of diamond ore ultimately converge on the same precision processing chain: crushing, washing, jigging or dense-medium separation, and X-ray sorting. This “mine-to-gem” value chain is a tightly integrated process where every step directly impacts recovery efficiency and the quality of the rough diamonds. If you require customized diamond processing equipment solutions, please feel free to contact us. We are here to help you achieve superior diamond production quality and ensure that the full value of every rough stone is realized.