Deposit types
Ore deposits form in a handful of recognisable ways. The deposit type tells you what size, grade, shape and mining method to expect.
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A deposit type is a family of ore deposits that formed in a similar way. Knowing the type tells you what a deposit is likely to look like before much drilling is done.
What it is
Metals are spread thinly through the Earth's crust. An ore deposit forms where a geological process, such as hot fluids, magma or weathering, concentrated them far above normal levels. Each process leaves a recognisable pattern. Geologists group deposits that formed the same way into a , sometimes called a deposit model.
The main types
| Type | Main metals | Typical size and grade | Shape | Usual mining method |
|---|---|---|---|---|
| Porphyry | Copper, gold, molybdenum | Very large (hundreds of Mt to billions of tonnes), low grade (0.3–1% copper) | Large, roughly cylindrical bodies | Open pit or block caving |
| Epithermal | Gold, silver | Small to medium; high-grade veins (often 5–20 g/t) or large low-grade bodies | Veins, vein swarms | Underground or open pit |
| Orogenic gold | Gold | Medium; 1–10 g/t | Veins and shear zones, often deep | Open pit, then underground |
| Volcanogenic massive sulphide (VMS) | Copper, zinc, lead, gold, silver | Small to medium (1–50 Mt), polymetallic, rich | Compact lenses, often in clusters | Mostly underground |
| Sediment-hosted zinc-lead | Zinc, lead, silver | Medium to very large; 5–15% zinc and lead combined | Flat-lying layers | Open pit or underground |
| Skarn | Copper, zinc, tungsten, iron, gold | Small to medium | Irregular, next to intrusions | Open pit or underground |
| Magmatic nickel-copper | Nickel, copper, platinum-group metals | Medium; 1–3% nickel | Lenses at the base of intrusions | Underground or open pit |
| Iron oxide copper-gold (IOCG) | Copper, gold, sometimes uranium | Large; about 1–2% copper | Breccia bodies | Underground or open pit |
| Laterite | Nickel, cobalt, aluminium (bauxite) | Large, low grade | Flat blankets near the surface | Shallow open pit |
| Pegmatite | Lithium, tantalum, tin | Small to medium; about 1–1.5% lithium oxide | Dykes and sheets | Open pit |
| Placer | Gold, tin, diamonds | Small | Gravels in rivers and old beaches | Dredging or open pit |
Why it matters
- Expectations: a porphyry at 0.4% copper can be world-class; a VMS at 0.4% copper is not worth mining. Grade and size only make sense against the type.
- Mining method and cost: the shape and depth of a deposit decide whether it can be mined cheaply from an open pit or needs underground mining.
- Metallurgy: each type has typical minerals and recovery issues.
- Exploration strategy: each type responds to different survey methods.
- Clustering: deposits of one type often occur in districts. A project next to a known deposit has better odds, but proximity alone proves nothing.
Ranges are indicative and vary by deposit and region. This is educational material, not investment advice.
Key terms
Next in this track
Exploration methodsBefore drilling, explorers narrow down where to look with mapping, geochemistry, geophysics and remote sensing. Each method finds different clues.Related articles
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Educational material only. Nothing here is investment advice or an offer to buy or sell any security or mineral interest.