Orogenic Gold
Gold-bearing quartz veins formed during mountain building, often along major shear zones. Typically mined underground or in open pits.
Gold Mining
Gold mining: from geology to doré
Gold is rare, dense and chemically stubborn. Finding it, extracting it and recovering it efficiently requires careful geological assessment and carefully engineered processes.
Why Gold
The enduring value of gold
Gold has been valued for thousands of years because it does not corrode, is easily worked and is genuinely scarce. Most commercially mined gold is present at grades of only a few grams per tonne of rock — meaning a tonne of ore may contain less gold than a small ring.
Today gold is used in jewelry, held by investors and central banks, and relied on in electronics, dentistry and aerospace for its conductivity and resistance to tarnish. Each use depends on a mining industry able to recover very small concentrations of metal from very large volumes of rock.
Geological Assessment
Understanding gold deposit types
The way gold was deposited controls where it is found, how it is mined and how it is recovered. Geologists classify deposits to guide exploration and evaluation.
Epithermal Deposits
Formed near the surface by hot fluids linked to volcanic activity. Can be high grade and are frequently rich in silver as well.
Porphyry Systems
Very large, lower-grade deposits where gold occurs with copper around intrusive rocks, usually mined by large open pits.
Placer Gold
Free gold eroded from primary sources and concentrated in river gravels, recovered using gravity methods.
Carlin-Type
Microscopic gold disseminated in sedimentary rocks, often requiring specialized processing to unlock.
Paleoplacers
Ancient, lithified placer deposits in conglomerates, some among the largest gold sources ever mined.
Resource Evaluation
From drill data to a mineable resource
Gold is notoriously erratic. A single coarse gold particle can make one sample look rich while its neighbor appears barren — the so-called nugget effect. Robust assessment therefore relies on dense drilling, careful sampling protocols and strict quality assurance.
Assay results, geological logging and structural interpretation are combined into a 3D model. Geostatistical methods then estimate tonnes and grade block by block, and qualified professionals classify the confidence of each part of the resource in line with recognized reporting codes.
- Duplicate, blank and certified reference samples for QA/QC
- Fire assay as the reference method for gold
- Metallurgical testwork to confirm recoverability
Mining Techniques
How gold ore is mined
Open-pit mining
Large tonnages of lower-grade ore near surface, mined in benches with high-capacity equipment.
Underground mining
Narrower, higher-grade veins accessed through declines or shafts and mined with selective stoping methods.
Alluvial mining
Placer gravels excavated and washed to recover free gold particles by gravity.
Gold Processing
Recovering gold from ore
The processing route depends on how the gold occurs — free and coarse, locked in sulfides or very finely disseminated.
| Method | Best suited to | How it works |
|---|---|---|
| Gravity concentration | Coarse, free gold | Centrifugal concentrators and tables separate heavy gold particles by density. |
| Flotation | Gold associated with sulfides | Reagents make sulfide particles attach to air bubbles, producing a gold-bearing concentrate. |
| Carbon-in-leach / carbon-in-pulp | Free-milling ores | Gold is dissolved in a controlled leach circuit and adsorbed onto activated carbon. |
| Heap leaching | Low-grade, oxidized ores | Crushed ore is stacked on lined pads and irrigated; gold-bearing solution is collected and processed. |
| Pressure oxidation / bio-oxidation | Refractory ores | Sulfides are broken down before leaching to release locked gold. |
| Elution & electrowinning | Final recovery | Gold is stripped from carbon, plated onto cathodes and smelted into doré bars. |
Leach circuits use reagents that must be handled under strict controls. Responsible operations follow recognized management codes, monitor water continuously and treat residues before storage. See Sustainability.
Responsible Production
Producing gold the right way
Responsible gold production goes beyond compliance. It means knowing where gold comes from, minimizing water and energy use per ounce, designing tailings facilities for long-term stability and working openly with neighboring communities.
It also means maximizing resource efficiency: improving recovery so that less ore must be mined, and planning extraction so that valuable resources are not sterilized by poor sequencing.
- Chain-of-custody and responsible sourcing principles
- Progressive rehabilitation of disturbed land
- Safe, engineered tailings management
Gold Mining FAQ
Frequently asked questions
How much gold is in typical ore?
It varies widely. Large open-pit deposits may be economic below one gram per tonne, while narrow underground veins often need several grams per tonne or more to cover their higher mining costs.
Why is gold so hard to recover?
Gold is often present as tiny particles or locked inside sulfide minerals. Grinding fine enough to expose it, and choosing a recovery method suited to its mineralogy, is the central challenge of gold metallurgy.
What is doré?
Doré is a semi-pure alloy of gold and silver poured at the mine site. It is shipped to a refinery, where it is purified to bullion standards.
How does gold relate to silver mining?
Many gold deposits also contain silver, and the two are often recovered together. Learn more on our Silver Mining page.
Discover how gold deposits are found
Every gold mine begins with exploration — geological mapping, sampling and drilling.