Types of Gold Deposits: Geology and Host Rocks

Gold deposits fall into five main types plus a group of minor styles: Witwatersrand-type ancient river placers, orogenic (mountain-building) deposits, porphyry, epithermal and Carlin-type. Together the first two hold about 61% of all the gold known to geologists, according to a Mineralium Deposita review by Frimmel and Hennigh (2015). The type matters because it controls the host rock, the shape of the orebody, how deep gold formed, and how the ore must be processed.

People often ask what the “types of gold rocks” are. Strictly, there is no single gold rock: gold is a trace component of quartz veins, conglomerate, black shale, schist, volcanic rock and river gravel. This guide covers both views, first the host rocks and then the deposit types, with the geology of each, a comparison table, world production data, a section on nickel, which is sometimes found in the same districts, and a gold calculator you can adjust.

Main types of gold deposits ranked by share of known gold

Geologists measure a deposit type by its endowment, meaning past production plus reserves plus resources. Frimmel and Hennigh, citing Frimmel’s 2008 compilation, report these shares of the world’s known gold in deposits: Witwatersrand-type 31%, orogenic 30%, porphyry 16%, epithermal 12%, Carlin-type 4% and all other types 7%. The chart below shows them. Treat the percentages as a scientific estimate from one published compilation, not an audited figure.

Chart

Share of known gold by deposit type

Percent of past production plus reserves plus resources

Production tells a different story from endowment. Carlin-type deposits hold only 4% of known gold, yet Cline and co-authors (2005) wrote that their output was about 9% of world production at the time. A type’s share of past production, of remaining resources and of new discoveries can all differ.

Gold host rocks: what the rock tells you

Field geologists name gold “rocks” by what surrounds the metal. Five host rocks are the most common settings for gold. Grade is quoted in grams per tonne (g/t), the mass of gold in each tonne of rock.

• Quartz veins in metamorphic and volcanic belts: the classic orogenic setting. At Kalgoorlie, Vielreicher and co-authors (2016) describe banded quartz-carbonate veins and pyrite-rich lodes in the Golden Mile Dolerite, a sill of altered igneous rock.
• Schist and shear zones: layered metamorphic rock cut by faults, as at Macraes in New Zealand, described below.
• Conglomerate: cemented pebble beds, the Witwatersrand style.
• Silty, carbonaceous limestone: the Carlin style, where gold is too fine to see.
• Volcanic rock and breccia: the epithermal style, often bleached and clay-altered.

A sixth class is loose gravel and soil, where weathering has released gold from the rock. If you are comparing what gold in rock looks like, our guide to rocks with gold specks covers visible gold, quartz and iron-stained rock in more detail. Visible gold is the exception: in Carlin ore and in much sulfide-hosted ore, the metal is invisible to the eye and needs an assay to detect.

Orogenic gold: veins in schist and greenstone

An orogeny is a mountain-building event. Orogenic gold deposits form when plates converge and squeeze water and gold out of rock as it is heated and deformed. Groves and co-authors (1998), in a paper held by the US Geological Survey library, describe deposits forming during compression at convergent plate margins, hosted in hydrated marine sedimentary and volcanic rocks that were added to continental edges. They split the deposits by depth: epizonal (under 6 km), mesozonal (6-12 km) and hypozonal (over 12 km).

Many orogenic deposits are very old. Frimmel and Hennigh note a peak in their formation between about 2.7 and 2.4 billion years ago (Ga means billion years ago; Ma means million years ago). Kalgoorlie, described next, lies in a granite-greenstone terrane, a belt of old volcanic and sedimentary rocks that was folded, metamorphosed and intruded by granite.

The Golden Mile at Kalgoorlie, in the Eastern Goldfields of Western Australia, is a giant example. Vielreicher and co-authors classify it as orogenic and mesozonal, say gold has been produced continuously since June 1893, and report that its bonanza lodes (called Oroya-style) reach grades above 1,000 g/t gold, with visible gold and tellurium minerals.

Gold in schist: the Macraes example

Schist is a layered metamorphic rock that splits into thin sheets. Gold in schist usually follows faults and shear zones rather than the layering alone. OceanaGold’s geology summary for Macraes, in New Zealand’s Otago Schist, describes the Hyde-Macraes Shear Zone: up to 150 m thick, at least 40 km along strike, dipping 10-20 degrees northeast, and formed at about 10 km depth and about 300 °C. OceanaGold gives the Macraes deposit an endowment of more than 10 million ounces (mined plus remaining), and the page dates it to roughly 140-130 million years ago.

The same summary explains the mechanism: metamorphism of thick marine sediments released fluids carrying gold, tungsten, arsenic and antimony into shear structures, and graphite created a reducing environment that precipitated sulfides and gold. The gold is mostly tiny grains inside pyrite and arsenopyrite (iron and iron-arsenic sulfides) or in quartz, with scheelite (a tungsten mineral) as a companion. That is a good example of why “gold in schist” is not one rock type but a structure-controlled orogenic system.

High-grade gold shoots inside orogenic lodes

A gold shoot is a zone of higher grade inside a vein or shear zone. At Macraes the gold is concentrated in thicker, higher-grade, plunging shoots separated by weakly mineralised sheared rock. At Kalgoorlie, Vielreicher and co-authors describe Oroya-style bonanza lodes above 1,000 g/t as the high-grade end of the same orogenic system. The Macraes summary credits a graphite-bearing, chemically reducing environment for making gold and sulfides drop out of the fluid and says the Footwall Fault forms the lower limit of economic mineralisation.

Witwatersrand-type gold: ancient river placers

A placer is a deposit in which flowing water has concentrated heavy gold grains. The Witwatersrand Basin in South Africa is the largest known example, a set of gold-bearing conglomerates (cemented gravel) laid down by rivers and deltas. Frimmel and Hennigh give its historic production as more than 52,000 t of gold, 32% of all gold ever mined, and reported reserves and resources of 16,400 t gold in 2014.

Where the gold came from has been argued for decades; Frimmel and Hennigh note that the lack of a suitable source was long the main argument against the placer model. They conclude that the chemistry of the Mesoarchaean atmosphere and oceans (the era about 3.2-2.8 Ga ago) sent a very high flux of gold off the land surface, and that it concentrated in nearshore sediments on unconformities, scour surfaces and bedding planes about 2.9 Ga ago. They also note that Witwatersrand production had fallen steadily for a quarter century by 2015.

Carlin-type gold deposits: geology and host rocks

Carlin-type deposits are named after the Carlin mine in Nevada, found in 1961. Cline and co-authors describe them as replacement bodies in silty carbonate rock, where hot fluids dissolved the carbonate (decarbonatization), added clay and, in places, silica. Gold sits in solid solution or as sub-micron particles in disseminated pyrite and marcasite, so it is called “invisible gold”.

The same paper gives the main facts geologists use to recognise the type:

• Age: the Nevada deposits formed about 42-36 million years ago.
• Depth and fluid: within a few kilometres of the surface, from moderate-temperature (about 180-240 °C), low-salinity fluids.
• Host rock: reactive, pyritic and carbonaceous silty limestones; the largest deposits lie beneath the Roberts Mountain thrust, a regional fault that placed less permeable rock above them.
• Size: several are world class (over 100 t of gold) and some giant (over 250 t), though grades and contents vary widely.
• Analogues: the authors note that deposits in southern China are remarkably similar.

The origin is not settled. Cline and co-authors say a comprehensive, widely accepted genetic model remains elusive, with models that credit meteoric water, nearby intrusions, or deep metamorphic or magmatic fluids. Nevada as a whole produced about 64% of US gold in 2025 (estimate), according to the USGS Mineral Commodity Summaries 2026; that figure covers all gold mining in the state, not only Carlin-type ore.

Epithermal gold deposits: shallow veins near volcanoes

“Epithermal” means formed at shallow depth. White and Hedenquist (1995) put the temperature range at under 150 to about 300 °C and the depth at the surface to as deep as 1-2 km. They report that most ore forms at 180-280 °C, about 100 m to 800-1,500 m below the ancient water table. The authors, writing in the Society of Economic Geologists newsletter, separate two main styles, which matter for exploration:

• Low-sulfidation (also called adularia-sericite): fluids close to neutral, mostly rainwater in origin, with open-space veins and an alteration halo of clay and adularia (a potassium feldspar).
• High-sulfidation (acid-sulfate): acidic fluids from magma near young volcanoes that leave vuggy quartz, a honeycomb rock, with kaolinite clay and alunite (a sulfate mineral) nearby.

An example is Tonopah in Nevada, which USGS Bulletin 1857-H describes as a quartz-adularia epithermal deposit of the silver-rich subtype, meaning its silver value exceeds its gold value. For districts, styles and exploration clues, see our guide to epithermal gold deposits, or the USGS bulletin itself.

Porphyry and intrusion-related gold deposits

A porphyry deposit is a large volume of rock cut by many small veins around a magma intrusion. The USGS porphyry copper model describes them as high-tonnage (over 100 million tons), low- to moderate-grade ores of 0.3-2.0% copper, with gold and molybdenum recovered as co-products at some deposits. Gold is therefore often a by-product: USGS reports that about 7% of US gold in 2025 (estimate) came from base-metal ores, chiefly copper, and that nearly one-quarter of US undiscovered gold resources are thought to lie in porphyry copper deposits.

Intrusion-related gold systems are a separate group. In a doctoral study of the Tintina Gold Province of Yukon and Alaska, Hart (2005) links the major deposits to reduced, ilmenite-series Cretaceous intrusions and lists Donlin Creek (12.3 million ounces), Pogo (5.8) and Fort Knox (5.4). Whether Pogo is intrusion-related or orogenic is debated: Taylor, Graham and Lowers (2024) note that it has been classified both ways and test it with monazite and xenotime chemistry. Take any deposit-type label as a working model, not a fact.

Placer gold: eroded lode gold in river gravel

Modern placer gold is lode gold that weathering and rivers have moved. The USGS bulletin on Arizona placers counted 87 placer districts that produced at least 564,052 ounces between 1774 and 1968, and traced most of that gold to small gold-quartz veinlets and stringers nearby. Placers are therefore clues to a lode source upstream. They are a surface product of the lode types above, not a separate category in the Frimmel and Hennigh shares.

Placers matter commercially in Alaska. USGS reports that Alaska produced about 22% of US gold in 2025 (estimate), from several large placer mines and many small ones. Small-scale panning needs permission from the landowner or claim holder, and mercury must never be used to collect gold.

Where gold deposits are mined today

USGS estimates world mine production at 3,300 t in 2025, up slightly from 3,280 t in 2024, with identified reserves of 66,000 t. China, Russia, Australia and Canada lead, and the United States ranks fifth. The dumbbell chart shows the seven largest producers. Within the United States, USGS puts Nevada first with about 64% of 2025 output and Alaska second with about 22%.

Chart

Seven largest gold-mining countries

Tonnes of gold, mine production, 2024 and 2025 estimate

For a ranked list with more detail, see our guide to the top gold-producing countries, the largest active gold mines in the USA and the largest gold mining companies. For element facts, see gold (Au) on the periodic table.

How deposit type changes mining and processing

Deposit type drives the mine plan. Narrow vein and shoot ores tend to be mined selectively, often underground, while wide, lower-grade bodies such as porphyry and large shear-hosted deposits tend to suit bulk open pits. Carlin-type ore varies widely in grade and content (Cline and co-authors, 2005), so the mining method is set deposit by deposit. Placers are dug or dredged. In every hard-rock case the ore is crushed and ground first; see our guide to rock crushing in mining for that step, and the iron ore processing guide for how another commodity is handled.

The bigger question is whether the gold is easy to recover by direct leaching or is refractory. Refractory ore has gold locked inside sulfide minerals, so cyanide cannot reach it directly. Pressure oxidation, roasting and biological oxidation are the treatments reviewed in a Society for Mining, Metallurgy & Exploration paper by Goode (1993). Sub-micron gold in pyrite, as at Carlin, and fine grains in pyrite and arsenopyrite, as at Macraes, are the kind of occurrence that can make ore refractory, but only metallurgical testing of the actual ore shows which route is needed.

Use the calculator below to scale a deposit: enter tonnes, grade and recovery to see contained gold, recovered gold and the gross value at a price you choose. Contained gold in tonnes equals million tonnes of ore times grams per tonne, which makes it easy to compare with the 100 t and 250 t thresholds that Cline and co-authors use.

▶ How gold is mined and refined, from rock to ring, with a clay nugget as the guide. · 5:27

Nickel deposits and how they relate to gold

Nickel shares some geology with gold, notably in Western Australia’s Eastern Goldfields. The two main nickel ore types are magmatic sulfide and laterite. The USGS Mineral Commodity Summaries 2026 estimate that world nickel resources exceed 350 million tons of nickel, with 54% in laterites, 35% in magmatic sulfide deposits, 10% in hydrothermal systems (iron-nickel alloy, sedimentary-hosted polymetallic and volcanogenic massive sulfide types, plus seafloor manganese crusts and nodules) and 1% in tailings and other resources.

Chart

World nickel resources by deposit type

Percent of more than 350 million tons of contained nickel

Magmatic sulfide nickel forms when a mantle-derived magma becomes saturated in sulfur and a separate sulfide liquid forms. Geoscience Australia authors Hoatson, Jaireth and Jaques (2006) describe the Australian cases: Archean komatiites (very hot ultramafic lavas) emplaced in rift zones of granite-greenstone belts, and mafic-ultramafic intrusions in older cratons. Their review dates the discovery of massive sulfides at Kambalda, in the Eastern Goldfields of Western Australia, to 1966, and puts Australia’s nickel sulfide resource at about 12.9 million tonnes of nickel.

That is the link with gold: Kalgoorlie’s Golden Mile and the Kambalda nickel field both lie in the Eastern Goldfields, and both sit in Archean granite-greenstone terrain, though they formed from different processes. The USGS compilation of sulfide models also notes that magmatic sulfide deposits supplied about 60% of world nickel in an older (2004) estimate, with most of the rest from laterites.

Laterite nickel is the weathered cap of ultramafic rock in humid tropical climates. The USGS database of nickel-cobalt laterites describes a profile from the top down: overburden, iron-rich ferruginous laterite (the “limonite zone”), saprolite, then the fresh rock. Garnierite, a nickel-bearing magnesium silicate, is listed in about a third of the 120 deposits in the database. On the production side, the 2026 USGS summary lists Indonesia at 2.6 million tonnes of the 3.9 million tonne world total in 2025 (estimate). Our laterite nickel ore guide covers the processing side.

How geologists tell the types apart

Exploration starts with simple questions. What is the host rock? How deep and hot did the fluid get? What alteration minerals surround the gold? The flow chart below puts the sequence in order.

Infographic

Identifying a gold deposit type in 5 steps

1. 1Name the host rockQuartz veins, schist, conglomerate, silty limestone or volcanic rock narrows the choices.
2. 2Estimate depth and heatAlteration and fluid data separate shallow, cooler systems from deep, hotter ones.
3. 3Read the alterationLeached limestone, adularia and clay, vuggy quartz, or quartz-carbonate veins point to a style.
4. 4Map the structuresShear zones, thrusts and fault intersections control where the ore sits.
5. 5Test how the gold is heldDirectly leachable gold, or gold locked in pyrite and arsenopyrite, decides the processing route.

Alteration is the visible side of the answer. In a Carlin-type system the clues are decarbonatized (leached) limestone, clay, and silica. Low-sulfidation epithermal systems carry adularia, sericite and clay in veins, while high-sulfidation systems leave vuggy quartz and acid clays such as alunite and kaolinite. Orogenic systems leave quartz-carbonate veins with sericite, carbonate and pyrite, as at Kalgoorlie. Satellite imagery cannot see gold itself, but multispectral and shortwave-infrared scenes can show iron-oxide staining, clay-rich zones and faults, which helps a consultant or licence holder rank ground before fieldwork. The Farmonaut satellite mineral detection page explains what the analysis delivers, and you can send a query about your project area or contact the team.

Whatever the type, classification is a model for choosing what to test next. Drill results, assays and a qualified person’s report decide whether a target is a resource. Always confirm claim, licence and access rules with the regulator for your jurisdiction before you sample.

▶ Why satellites cannot see gold, and how they map the rusty stains, clay and faults around it. · 4:25

For the same framework across all metals, see types of ore deposits, with grades, tonnages and example deposits.

Frequently asked questions

What are the main types of gold deposits?

The main types are Witwatersrand-type paleoplacer, orogenic, porphyry, epithermal and Carlin-type, plus a group of other styles. By share of known gold, Frimmel and Hennigh (2015) give 31%, 30%, 16%, 12%, 4% and 7% respectively.

What are the types of gold rocks?

Gold is hosted by quartz veins, schist and shear zones, conglomerate, silty carbonaceous limestone and volcanic rock, and it is also found loose in river gravel. Each host rock goes with a deposit type: veins and schist with orogenic, conglomerate with Witwatersrand-type, limestone with Carlin-type and volcanic rock with epithermal.

What is the geology of Carlin gold deposits?

Carlin-type deposits are replacement bodies in reactive silty limestone. In Nevada they formed about 42-36 million years ago within a few kilometres of the surface from fluids of about 180-240 °C. The gold is sub-micron and held in pyrite. The source of the fluids is still debated (Cline and co-authors, 2005).

What is orogenic gold?

Orogenic gold deposits form during compression at convergent plate margins, in metamorphosed volcanic and sedimentary rocks. They span a wide depth range, from epizonal (under 6 km) to hypozonal (over 12 km), according to Groves and co-authors (1998).

Is gold found in schist?

Yes. At Macraes in New Zealand the gold is in a shear zone up to 150 m thick inside the Otago Schist, mostly as tiny grains in pyrite and arsenopyrite, in a deposit of over 10 million ounces, per OceanaGold’s geology summary. The gold follows faults, so it is not spread evenly through the schist.

What is a high-grade gold shoot?

A shoot is a zone of higher grade inside a vein or shear zone. At Macraes, gold concentrates in thicker, plunging shoots separated by weakly mineralised rock. At Kalgoorlie, the bonanza (Oroya-style) lodes exceed 1,000 g/t.

What is the difference between lode and placer gold?

Lode gold is still in its host rock, in veins or disseminated through it. Placer gold has been released by weathering and carried by water into gravel. Most placer gold in the Arizona bulletin traced back to nearby veinlets.

What is refractory gold ore?

It is ore in which the gold is locked in sulfide minerals such as pyrite and arsenopyrite, so ordinary cyanide leaching recovers little. Treatments include pressure oxidation, roasting and biological oxidation.

How does epithermal gold differ from orogenic gold?

Epithermal gold forms close to the surface, at under 150 to about 300 °C, near volcanoes. Orogenic gold forms deeper in metamorphic belts. Epithermal ore is often found in volcanic rock; orogenic ore in schist, greenstone and quartz veins.

How do geologists explore for gold ore deposits?

They map host rocks and structures, sample soil and rock, read the alteration minerals, and drill. Satellite imagery can screen large areas for iron staining, clay and faults before fieldwork, but only drilling and assays prove gold.

Is nickel found with gold?

Sometimes in the same district. Kambalda nickel sulfides and the Kalgoorlie Golden Mile are both in Western Australia’s Eastern Goldfields, though they have different origins. Most nickel resources, 54% by USGS, are in tropical laterites rather than in gold camps.