Alluvial Gold Mining: Methods, Recovery and Break-even

Alluvial gold mining recovers gold grains from river sand and gravel by washing the gravel and letting gravity catch the heavy metal. The method works best on coarse gold: a well-run sluice box catches over 95% of 1 mm gold but under 20% of grains finer than 0.1 mm, according to British Geological Survey (BGS) work published in 2021. Whether a creek pays then comes down to three numbers: grams of gold per cubic yard of gravel, the share your plant recovers, and the gold price. This guide covers the methods, the equipment, recoveries, costs, permits and water rules, with a calculator for your own ground.

How alluvial gold mining works

Alluvial gold (also called placer gold) is gold that rivers have eroded from its source rock and dropped in gravel, sand and silt. The gold is the same metal as lode gold. It is often cleaner: in Alaska most placer gold runs from 800 to 900 fine, meaning 80 to 90% gold with silver as the main impurity, and the state average is about 892 fine (BLM Alaska placer guide, 2026). So “raw alluvial gold” is real gold, sold on its fineness. For the geology of how these deposits form, read What Is a Placer Gold Deposit?. This page is about the mining side.

Every alluvial operation, from a pan to a dredge, follows the same logic. Dig the gold-bearing gravel (often called pay gravel or paydirt), break up clay, remove oversize rock, then use water to separate the heavy gold from lighter sand. Grade is stated in grams of gold per bank cubic yard (BCY), meaning a yard of gravel measured in the ground before it is dug. The BLM guide gives a worked example: 100,000 BCY at 0.4 g per BCY holds 40,000 g, or about 1,286 troy ounces (31.1 g to the ounce).

Gold sits low in the gravel. The Washington Department of Natural Resources notes that placer values are almost always concentrated on or near bedrock, and that large amounts of gold have been recovered by cleaning bedrock carefully in old districts (Washington DNR, Open File Report 79-0). That is why pits are dug to bedrock and why bedrock cleanup is a separate, careful job.

Where alluvial gold is found

Gold collects where fast water slows down. The Washington survey lists broader valleys below narrow gorges, tributary junctions, the heads of quiet reaches and the inside of stream bends. Old terraces and bars well above today’s river hold gold too, because the river once ran there. Look for the same spots when you read a map of a creek, then confirm with samples.

Production comes from many countries. Alaska produced about 22% of US gold in 2025, with several large placer mines and many small ones in Alaska and the western states, while the world mined an estimated 3,300 tonnes of gold in 2025, with Ghana at about 150 tonnes (USGS Mineral Commodity Summaries, 2026). The USGS figures cover all gold, not only alluvial. In the Yukon, the Dawson City area around the Klondike generated the highest gold production revenue ever recorded in 2024 (about C$284 million from nearly 99,000 crude ounces, as reported to spring 2025), according to the Yukon Geological Survey as quoted by CBC News (9 September 2025).

In Australia, the NSW Resources Regulator names Wallaby Rocks near Sofala among the creek sites it inspected for illegal fossicking, and the rules on who may dig, and with what, are strict. See the permits section below. For legal panning spots and rules by land type, see Can You Pan for Gold in California?, and for Alaska claims see How to Get a Gold Claim in Alaska.

Alluvial mining methods compared

The methods differ mainly in how much gravel one crew can wash in a day and how much paperwork they bring. The throughput numbers below are for hand work and come from the Washington survey; larger plants are sized to the pit and the permit, not to a rule of thumb.

Surface methods for hard-rock gold are a different topic and are compared in Methods for Mining Gold: 5 Surface Methods Compared.

Sluices, trommels and wash plants

A modern wash plant has three jobs: feed the gravel at a steady rate, remove the rock that cannot carry gold, and run the rest over a gravity recovery circuit. The BLM Alaska guide describes the main classification tools. Shaker screens use vibration and water spray and can pass more material than a trommel. A trommel is a rotating drum lined with screens; it handles smaller quantities for its size but is very good at breaking up clay and cemented gravel. A grizzly is a set of heavy bars over the feed hopper that keeps boulders out. A derocker suits deposits with many large boulders, but it classifies less cleanly.

Infographic

Wash plant circuit in five steps

1. 1Dig to bedrockStrip overburden and load pay gravel.
2. 2Remove bouldersGrizzly bars or a derocker keep large rock out.
3. 3Screen and break clayTrommel or shaker screen sizes the feed.
4. 4SluiceRiffles and matting trap gold by gravity.
5. 5Clean upConcentrate is panned or tabled; tailings go to settling ponds.

After screening, the slurry goes to sluice boxes. They have been used in Alaska since the gold rush and are relatively inexpensive and low in maintenance (BLM Alaska guide). Matting or riffles in the bed trap the gold. BGS describes angle iron or expanded metal riffles that create a vortex-like layer along the bed, which acts like a small centrifugal separator (BGS technical report CR/02/029N).

Plants that recycle water add sand screws and hydrocyclones. The BLM guide says these help water treatment, let cleaner water return to the plant, and make tailings easier to handle and reclaim.

▶ How gold is mined and refined, step by step, from rock to ring. · 5:27

How a sluice box recovers gold, and what it misses

Recovery depends on the size of the gold. BGS reports that alluvial gold is typically 300 to 1,500 microns, while gold from hard-rock greenstone ore is often finer than 100 microns. A well-run sluice box recovers more than 95% of 1 mm particles, but under 20% of particles finer than 0.1 mm (BGS, 2021). The same paper says typical feed is about 9% solids (weight/volume) in water, recommends channels at least 3 metres long, and a deck sloped between 5 and 15 degrees from horizontal.

Chart

Expected sluice box recovery by gold size

Well-operated sluice box, share of gold caught (BGS says over 95% for 1 mm and under 20% for gold finer than 0.1 mm)

Three practical points follow. Test your gold size before you buy a plant, because fine gold needs another circuit, such as a shaking table, which BGS says can recover gold as fine as 15 microns. Keep the bed clean and the slope even, since breaks in the bed interrupt flow and lower recovery. And remember the gold left in tailings: In its Kenyan hard-rock study, BGS found artisanal miners re-run their tailings several times because they know a good part of the gold gets through; the lesson holds for any plant that loses fine gold.

The Washington survey adds a simple field check: black sand, the heavy dark grains that travel with gold, tells you how well the box is working. If black sand is caught, gold of similar weight should be caught too.

Dredges: suction and bucket-line

A suction dredge is a portable sluice on a float, fed by a suction hose that vacuums gravel from the stream bed. It reaches gold in places a shovel cannot, which is why it spread among small-scale miners. It also disturbs the stream bed, so regulators control it. In Oregon, the Department of Environmental Quality covers motorized suction dredges up to 30 horsepower with hoses no larger than four inches under its 700-PM general permit, and operators must register and have approval (Oregon DEQ 700-PM fact sheet). Always check the state and federal rules for the exact stream. The BLM Alaska guide has a full chapter on freshwater suction dredging and highbanking.

Bucket-line dredges are the industrial version. In the Klondike a dozen dredges worked at the peak, and the last of the Yukon Consolidated Gold Company dredges shut down in 1966 (Parks Canada, Dredge No. 4). Today’s equivalent is a fleet of excavators, trucks and a wash plant working in a contained pit, because modern permits limit how far streams can be disturbed.

Alluvial gold mining costs and break-even

The BLM guide splits cost into three groups: capital spending to reach steady production, operating spending once gold is being sold, and closure and reclamation including monitoring until final approval. It advises running worst, base and best cases, from the lowest expected gold price with the highest costs to the highest price with the lowest costs. Property, exploration and evaluation, and permits all sit in the list too, so a plant price alone understates what it takes to start.

Chart

Average gold price, US$ per troy ounce

USGS annual averages; 2025 is an estimate

Chart

Loose cubic yards of gravel per ounce that Yukon miners say can pay

Higher means thinner ground can still be worked. 100 = one ounce per 100 yards of sluice ground (past); 200 = half an ounce per 100 loose yards (calculated)

The gold price moves the break-even more than any equipment choice. The USGS records an average price of US$1,801 per troy ounce in 2021 and an estimated US$3,300 in 2025. Kitco listed spot gold at US$4,028.10 per troy ounce at 10:50 a.m. Eastern time on 29 October 2026 (Kitco).

In the Yukon, that price change has changed what counts as pay ground. The Yukon Geological Survey’s Sydney van Loon told CBC that miners once needed about one ounce per 100 yards of sluice ground to break even, and that half an ounce per 100 loose cubic yards is now doable. Placer miner Tim Osler said people now work ground that may be 150 yards per ounce and still make money. One ounce per 100 yards is about 0.31 g per yard; half an ounce is about 0.16 g. Note that these are loose yards. Loose gravel takes more space than bank gravel, so check which basis any quoted grade uses.

The same CBC report shows who benefits: the Yukon royalty on placer gold is just over 37 cents an ounce, a rate set in 1906 when gold was valued at $15 an ounce, and a Yukon economic development official said he expects it to be updated with new mining legislation. If you are reading a deal, check the royalty and fees in force on the day.

The calculator below turns your own numbers into recovered ounces, revenue, operating margin and the grade at which the gravel stops paying. Its default values are round examples, not benchmarks, so replace each with a sampled grade, a tested recovery and a quote for your own costs.

Permits, licences and water rules

Permits decide more alluvial projects than geology does. A few examples show the pattern.

Alaska: every modern commercial placer operation files the Application for Permits to Mine in Alaska (APMA), a single form that starts the state permits (BLM Alaska guide). The state’s APMA page says approvals run for one to ten years and a reclamation bond is required for disturbances over 5 acres (Alaska DNR, APMA). Federal land and water permits can add steps; see the BLM guide for the agencies involved.

Oregon: in-water placer mining and suction dredges fall under a general water permit that requires registration, as covered above. For claim costs and checks there, see Gold Claims for Sale in Oregon.

New South Wales: fossicking is allowed but tightly regulated. Only hand-operated tools such as gold pans, sieves, small shovels, pickaxes and metal detectors are allowed, power equipment such as pumps and excavators is banned, and fines of up to A$750 can apply (NSW Resources Regulator). Fossicking is not commercial mining; running a plant needs a mining title from the regulator.

Africa: the video below covers whether foreigners can get a small-scale mining licence, which depends on each country’s law.

Prospecting safety: get permission from the landowner or claim holder, hold the licence the regulator requires, stay out of other people’s claims, and never use mercury. Recovery without mercury, using sluices and shaking tables is covered in the next section. This page is for general information; confirm every rule with the regulator.

▶ Whether a foreigner can get a small-scale mining licence in Africa. · 5:16

Sustainable alluvial mining: water, mercury and reclamation

Alluvial mining moves sediment, so the main controls are about water. Settling ponds hold fine silt back from the stream, sand screws and hydrocyclones make recycling easier, and reclamation returns the pit to a stable shape. The BLM guide covers settling pond and stream reclamation as separate chapters and recommends a rolling footprint, in which mined ground is reclaimed behind the working face rather than left to the end. More on low-impact practice is in eco-friendly mining techniques, and on local benefit in community mining.

Mercury is the second control. BGS records that small-scale miners often amalgamate gold with mercury and burn the amalgam in the open, which sends mercury vapour into the air. Its guidance is to use a mercury retort, a sealed vessel that condenses the vapour, and better gravity circuits so that less mercury is needed. In Kenya, where BGS ran this hard-rock study, artisanal mining employs an estimated 40,000 people and produces 5 tonnes of gold a year and is a party to the Minamata Convention on Mercury, which it joined in 2017.

Better recovery is also a sustainability measure. Gold that the box already caught is gold you do not have to dig again, and every extra cubic yard stripped costs fuel, water and reclamation.

Screening alluvial ground from space

Satellite imagery cannot see gold grains in gravel. It can show old channels, terraces, bare workings and water, which helps you decide where to sample first, and it can document ground before and after work. Farmonaut maps a licence boundary from satellite data to show these features; the details are in satellite-based mineral detection, and you can request a quote for your area. Imagery narrows where to look; samples and assays still decide whether the gravel pays.

Frequently asked questions

What is alluvial gold mining?

It is the recovery of gold from river sand and gravel using water and gravity: digging pay gravel, screening out rock, and running the rest over sluices or other gravity equipment. The BLM Alaska guide lists the circuit as classification followed by gravity recovery.

Is alluvial gold real gold?

Yes. It is natural gold with silver as the usual impurity. Alaskan placer gold is mostly 800 to 900 fine, and refiners pay for the fine gold content (BLM Alaska guide).

Where is alluvial gold found?

In river beds, bars, bends, terraces and the gravels below gorges and at tributary junctions, usually concentrated near bedrock (Washington DNR). Well-known areas include the Klondike in the Yukon and placer districts across Alaska.

How much gold does an alluvial gold mine recover?

It depends on grain size. A well-run sluice box recovers over 95% of 1 mm gold but under 20% of gold finer than 0.1 mm (BGS, 2021). Total yield also depends on the grade of the ground, which is sampled in grams per cubic yard.

What is the best alluvial mining method?

There is no single best method. Pans and sluices suit sampling and small claims, suction dredges reach stream beds but need water permits, and screened wash plants suit larger, permitted pits. Choose by gold size, volume of gravel and the permits you can get.

What is alluvial gold ore?

Alluvial gold is not mined as hard rock ore. The material is loose gravel, sand and clay, sometimes called pay gravel, graded in grams of gold per bank cubic yard.

Is there alluvial gold in NSW and can I dig for it?

The NSW Resources Regulator has investigated suspected illegal fossicking at creek and bridge sites including Wallaby Rocks near Sofala, Gilmore Creek near Tumut and Rocky Creek Bridge near Bathurst and Orange. Fossicking is limited to hand tools and power equipment is banned (NSW Resources Regulator). Commercial work needs a mining title. Check the rules with the regulator before you go.

What are the disadvantages of alluvial mining?

Fine gold escapes simple sluices, water and sediment need management, mercury use harms health and rivers, and permits can be slow. Good plant design, settling ponds and water recycling reduce the impact.

How much does it cost to mine alluvial gold?

Costs split into capital, operating and closure items (BLM Alaska guide) and vary widely with site and equipment, so this page does not quote a single per-yard figure. Use sampled grade, tested recovery and your own quotes in the calculator above; the break-even grade it returns is the number to compare with your samples.

Can alluvial gold mining be sustainable?

Yes, where water is recycled, silt is settled out, mercury is replaced by gravity methods and retorts, and pits are reclaimed as work advances. The BLM Alaska guide describes a rolling footprint and settling pond reclamation for exactly this reason.