Placer Deposit: Where They Form, Grades and Value

A placer deposit is a body of sand and gravel in which heavy, durable minerals such as gold have been concentrated by moving water. A placer gold deposit forms when a river, a beach or a hillside slope washes away lighter material and leaves gold behind. The U.S. Geological Survey says gold lags behind in stream beds because of its weight, and that as much as 90% of the gold recovered from stream placers sits in the lowest 3 feet of gravel and the top foot of bedrock (USGS Fact Sheet 058-98). This guide covers how placers form, where the famous districts are, how grade is measured in grams per cubic metre and ounces per cubic yard, and how to work out what a deposit is worth. For the digging and washing itself, see our guides to alluvial gold mining and surface mining methods for gold.

What a placer deposit is and how it differs from lode gold

Geologists split gold deposits into two broad groups. A lode deposit is the primary rock source, such as a quartz vein, that is still in place. A placer is a secondary deposit made of gold that weathering and erosion have broken out of a lode, carried away and sorted by water or wind (USGS Open-File Report 02-303). The same report lists the minerals that typically survive long enough to form placers: native gold, native platinum, cassiterite (tin oxide), monazite, zircon, rutile and magnetite.

Three differences matter to anyone buying, staking or valuing ground:

• Shape. A lode is a vein or zone that goes down; a placer is a flat or gently sloping layer of loose gravel near the surface.
• Gold form. Placer gold is loose grains, flakes and occasional nuggets. USGS notes that most placer gold in Alaska is flattened fragments less than 1/8 inch across and that nuggets are rare.
• Evaluation. Placer ground is sampled by volume of gravel and quoted in grams or ounces per cubic metre or yard. Lode ore is usually quoted in grams per tonne.

How a placer deposit forms: weathering, transport and traps

Placer geology follows a simple chain. Rock weathers, gold is liberated, water carries it, and gold drops out wherever the flow loses energy. Because gold is far denser than the quartz and feldspar around it, even a modest slowing of the current is enough to leave it behind. USGS lists the usual traps in stream beds: the inside of river bends, deep pools downstream of rapids and the downstream side of large boulders (USGS Fact Sheet 058-98).

Infographic

How a placer forms in 5 steps

1. 1Source rockGold sits in a vein or rock that is exposed at the surface.
2. 2WeatheringRain, frost and rivers break the rock and release the gold.
3. 3TransportWater carries gold downstream with sand and gravel.
4. 4TrappingGold drops where flow slows: bends, pools and behind boulders.
5. 5Pay streakRepeated reworking leaves rich gravel on or just above bedrock.

Three more points explain why placers are patchy:

• Repeated reworking. Stream placers are built by sands and gravels being moved and re-sorted many times, so the richest layer is often a thin, winding pay streak rather than the whole gravel body.
• The bedrock floor. Gold sinks through gravel until it meets bedrock, then lodges in cracks and rough spots. That is why the lowest gravel and the top of the bedrock carry most of the metal.
• Distance does not prove the source. The Alaska fact sheet warns that ragged, fresh-looking gold is not necessarily close to its source, because it may have been released from older sedimentary rock that had already travelled a long way.

Types of placer deposits and where each sits in the terrain

Placers are grouped by the process that made them. The table gives the common types and a sourced example for each where one exists.

USGS notes that wind as well as water can sort and concentrate placer minerals, but the water-laid types above are the ones that matter for gold.

Where placer deposits are found: famous districts

A placer needs three things in the same river system: a gold-bearing source upstream, enough relief to erode it, and a place for the gravel to collect. That combination gives a handful of districts that every placer guide returns to.

If you want to see these districts alongside lode mines, our world gold mines map is a good companion. For Alaska claim rules, see Alaska gold claims.

The Klondike strike was in Yukon, not Alaska, but the rush carried miners down the Yukon River to Alaska’s interior and to Nome. Alaska’s placers are still worked, and USGS says its Fortymile studies indicate gold remains to be found in that region.

How big placer gold is in world supply

Placers supplied almost all of the world’s gold in the early 1850s and now supply a small share. Data compiled by Kettel and reproduced in a USGS gold profile show alluvial gravels falling from 90% of world production in 1850-1875 to 8% by 1929, as quartz veins and cemented conglomerates took over (USGS Open-File Report 02-303).

Chart

Placer share of world gold production

Percent of world production from placer and alluvial gravels

Totals across history depend on how paleoplacers are counted. The USGS Alaska fact sheet says as much as two-thirds of all gold ever mined may have come from placers. Singer’s 1995 compilation, cited in the same gold profile, puts conventional placer at 11% of the gold found in deposits worldwide and counts Witwatersrand-type conglomerate separately at 42%. In the United States, placers were 14% of gold mined through 1998, and about 1% of mine output at the end of the 1990s.

The picture has moved again with high prices. Yukon’s geological survey attributes record production value in the 2024-25 fiscal year to high gold prices, good weather and increasingly large-scale operations (CBC News, September 2025).

Placer deposits of tin, platinum, diamonds and heavy minerals

Gold is only the best-known placer metal. The same sorting by weight concentrates other durable heavy minerals, and several are major commercial sources:

• Tin. Cassiterite is heavy and chemically inert, so it collects in eluvial and stream placers close to the granites that shed it. Placers gave about 70% of world cassiterite concentrate in 2012 (USGS). Our cassiterite and tin ore guide covers the market.
• Platinum. Native platinum is listed among the minerals that form placers, and the Alaska placer guidebook says platinum deposits need similar grade and purity calculations to gold.
• Gems. The Alaska fact sheet lists diamond, ruby and sapphire as placer minerals. Alluvial gem and diamond digging is common in Africa and South America.
• Heavy-mineral sands. USGS lists zircon, rutile, monazite and magnetite among the minerals that form placers, and beach sands rich in them are mined in several countries.

Placers are loose and often near the surface, which is why small operators can work them with simple equipment. The same looseness makes grade patchy, so each of these minerals needs sampling before any money is committed.

Placer grade explained: grams per cubic metre and ounces per cubic yard

Grade is the weight of gold in a standard volume of gravel. In metric countries it is grams per cubic metre (g/m³). In the United States and Canada it is traditionally ounces or grams per cubic yard. The Alaska placer guidebook from the Placer Mining Resource Network states that U.S. resource estimates are usually made in grams of gold per bank cubic yard (BCY), the volume of gravel in the ground, while the gravel run through the plant is counted in loose cubic yards (LCY). Gravel swells by about 14% when dug (Alaska Placer Mining 101 Guidebook, March 2026).

The conversions below use 1 cubic yard = 0.7646 cubic metres and 1 troy ounce = 31.1035 grams.

The PMRN guidebook gives a worked example. A deposit of 100,000 BCY at 0.4 grams per BCY holds 40,000 grams, or about 1,286 troy ounces. At the guidebook’s example fineness of 892, that is about 1,147 payable ounces. Always check whether a quoted grade is per bank or per loose yard before you compare two deposits, because the 14% swell alone moves the number.

What is a good placer gold grade?

There is no universal cut-off, because it depends on the gold price, the cost of moving and washing gravel, and how much waste lies on top. A Yukon Geological Survey geologist told CBC that miners once needed about one ounce per 100 loose cubic yards to break even, and that miners on the creeks now say half an ounce per 100 loose cubic yards is workable at current prices (CBC News, September 2025). That is roughly 0.41 g/m³ falling to 0.20 g/m³ of loose gravel. It is a miners’ rule of thumb relayed in a news report, not a standard.

Chart

Gross gold value per cubic metre of gravel

US$ per m³ by grade, at US$129.50 per gram (spot US$4,028.10/oz, 29 October 2026)

The chart turns grade into gross value so you can see how steeply it climbs. It uses the Kitco spot price of US$4,028.10 per troy ounce on 29 October 2026, which is about US$129.50 per gram (Kitco). Spot moves every day, so use the calculator below with the price on the day you read this.

These are gross figures. They ignore recovery losses, gold purity, stripping, labour, fuel, royalties and tax. Ground that looks rich on paper can still lose money if it sits under deep overburden or needs scarce water.

Placer gold purity and fineness

Placer gold is gold alloyed mainly with silver, and its purity is stated as fineness in parts per thousand. Fineness changes from creek to creek, and sometimes along one creek. A University of Alaska study of mint-return records from 550 Alaska creeks with more than 100 troy ounces of production found a mean fineness of 889, with individual creeks from 567 to 995 (Metz and Hawkins, MIRL Report 45, 1981). The regional means were close together, so the chart looks flat. The spread within a region matters more than the gap between regions.

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Alaska placer gold fineness by region

Mean fineness (parts of gold per 1,000), 550 creeks

Fineness converts directly into money. Gold of 892 fineness is 89.2% gold, so a refiner pays for 0.892 troy ounce of pure gold per ounce delivered, before any refining charges (Alaska Placer Mining 101 Guidebook). When you see a placer gold price quoted per ounce, check whether it is for pure or raw gold.

How much a placer deposit is worth: payable gold and break-even grade

Value is a chain of four numbers: the volume of pay gravel, its grade, the share you recover, and the purity of what you recover. Multiply them, convert grams to ounces and apply a price. The calculator does that and adds one cost input, so it also shows the break-even grade at your price. Costs vary widely with terrain, climate and scale; the cost figure in the form is only a placeholder for you to replace.

Two cautions apply to every placer valuation. The first is the nugget effect: in deposits with coarse, patchy gold a small sample can miss a nugget or catch one, so grade from a few pans is unreliable. The second is that the Alaska guidebook recommends using the lesser of the current gold price or the three-year trailing average when testing whether a mine would pay, because prices can fall during the life of an operation.

How to evaluate a placer deposit before you spend money

A sound placer evaluation moves from cheap, wide checks to expensive, narrow ones. The guidebook names three core exploration methods: drilling, test pits and trenching, laid out in rows (fences) across the valley, with closer spacing where pay streaks are narrow or grades vary a lot (Alaska Placer Mining 101 Guidebook).

1. Read the geology and records. Look up government survey reports and past production for the creek. Check fineness records, as above, and the thickness of overburden.
2. Map the ground. Identify the valley floor, terraces, old channel courses and the source rock upstream. Satellite and aerial images are useful here because terraces, drainage patterns and old workings show up at scale. Imagery cannot see gold itself; it shows where to sample first. Farmonaut offers satellite screening of a licence area for exploration targets; you can send an area through the mining query form or contact us for a quote. For the wider method, see satellite-based mineral detection.
3. Pan and sample the streams. Panning gives presence, colour and grain size, not grade.
4. Dig test pits or drill fences. Record method, location, depth, material type and groundwater for every sample, and scale each result to grams per loose cubic yard so samples of different sizes can be compared.
5. Take a bulk sample. A larger run through a small plant tells you recovery and the size distribution of the gold.
6. Estimate volume, overburden and water. Pay thickness, stripping volume and water supply decide the cost per cubic metre as much as grade does.
7. Work out fineness and payable ounces. Have the gold assayed or refined so the price you use is the price you will be paid.
8. Check ownership and permits. Confirm who holds the claim or licence, the surface rights and what permits an operation would need.

For the claim steps in California, our California gold panning laws guide is a starting point, and our guide to types of ore deposits shows where placers fit among the main deposit families.

▶ How satellite remote sensing helps screen ground for gold, and what it cannot see. · 4:25

How placer gold is recovered

Recovery methods follow the size of the deposit. Hand panning and sluice boxes suit small, shallow ground. Highbankers and trommels suit moderate volumes. Dredges and excavator plants suit large, wet or deep gravels. USGS describes the 20th-century shift in Alaska from hand tools and hydraulic hoses to steam shovels, bucketline dredges and later diesel equipment, which made lower-grade ground economic. The comparison of methods, costs and recovery rates is in our guides to alluvial gold mining methods and surface mining for gold, so it is not repeated here.

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

Permission, safety and environmental rules for placer ground

Placer ground is often a river valley, so water and land rules are strict. Alaska’s placer operations are required to use settling ponds to catch muddy runoff, and many recycle their wash water (USGS Fact Sheet 058-98, 1998). Whatever the country, get the landowner’s and regulator’s permission before you dig, hold the right licence or claim, keep to site safety rules, and never use mercury to collect gold.

▶ The seven main environmental impacts of mining, explained in clay. · 2:31

Frequently asked questions

What is a placer deposit?

It is a natural accumulation of heavy minerals in loose sand and gravel, left behind when water sorted the material by weight. Gold, tin, platinum and gemstones are the usual targets.

What is placer gold?

Placer gold (said “plass-er”) is gold that has weathered out of its bedrock source and been carried and concentrated in river, beach or hillside sediment. It occurs as flakes, grains and occasional nuggets.

What is the difference between placer gold and lode gold?

Lode gold is still in the rock where it formed, usually in veins. Placer gold has been released and moved. Lode ore is mined and crushed; placer gravel is dug and washed.

Where are placer deposits found?

Along rivers and creeks downstream from gold-bearing rock, on terraces and benches above them, in buried ancient channels, and on beaches. Well-known districts include the Klondike, Alaska, California’s Sierra Nevada, Victoria in Australia and the Witwatersrand.

What is an alluvial gold deposit?

It is a placer laid down by flowing water in a stream or floodplain. Geoscience Australia describes alluvial gold as secondary deposits that form when creeks wash gold out of eroding veins and concentrate it in hollows and the river bed.

What grade of placer gold is worth mining?

It depends on price and cost. A Yukon geologist relayed that miners now consider about half an ounce per 100 loose cubic yards workable, roughly 0.2 g/m³, where one ounce per 100 yards was once the break-even rule. Test your own ground against your own costs.

How much is placer gold worth?

Multiply payable grams by the gold price per gram. On 29 October 2026 Kitco’s spot price was US$4,028.10 per troy ounce, about US$129.50 per gram. A gravel with 0.4 g/m³ of pure gold carries about US$52 of gross metal per cubic metre before purity, recovery and costs.

How pure is placer gold?

Alaska placer gold averages about 889 fine (88.9% gold) across 550 creeks, with a range of 567 to 995. Other districts differ, so assay a sample.

What is a pay streak?

A pay streak is the narrow, richer band of gravel inside a placer, often following the old channel along bedrock. Most of the gold in a stream placer sits in the lowest 3 feet of gravel and the top foot of bedrock.

Can satellites find placer gold?

Satellites cannot see loose gold. They can map river terraces, old channels, drainage and disturbed ground, which narrows where field sampling should start.

Is placer mining the same as alluvial mining?

The two terms overlap. Alluvial mining refers to working stream-laid gravels, while placer mining also includes beach and eluvial deposits. See our alluvial gold mining guide for methods.