Flour Gold

Not all gold comes in flakes you can pick up with tweezers. A lot of it is dust so fine you need a lens to see it, and some of it will float right out of your pan if you are not careful. That is flour gold. This guide covers what it is, how small it is, where it collects and how to keep it in your pan.

What is flour gold?

Flour gold is the smallest gold a panner deals with: tiny, thin specks that look a bit like dust in the bottom of the pan. The U.S. Forest Service and Bureau of Land Management describe it in their panning guide as the finest gold dust, and they point out that much of it will float.

It gets that way by traveling. Gold that tumbles a long way downstream gets beaten flat and smooth, and the smallest pieces end up only a few microns thick. That is thinner than a sheet of paper by a long way.

How small is flour gold?

There is no single official cutoff, and different sources draw the line in different places. The clearest official scale we found is in the Forest Service and BLM panning guide. It sorts gold into four sizes. Coarse gold is anything over 2 mm, big enough to pick up with your fingers. Medium gold runs from 0.9 to 2 mm, about 2,200 pieces to a troy ounce. Fine gold is 0.4 to 0.9 mm, about 12,000 pieces to the ounce. Flour gold is everything under 0.4 mm, and it takes about 40,000 of those specks to make a troy ounce.

Other sources set the line a little differently. The Alberta Geological Survey, for example, describes flour gold as roughly 0.1 to 0.5 mm. Online stores often quote screen mesh sizes instead. Treat all of these as rough guides rather than a rule.

Some flour gold is far smaller than any of those numbers. In gravel from the Snake River, a USGS report found that about 90 percent of the gold was fine enough to pass through a 230 mesh sieve, and a single grain weighed only about 1 to 6 micrograms.

What does flour gold look like?

Like a dusting of tiny yellow specks in the bottom of your pan, often mixed in with black sand. Each one is flat and smooth rather than chunky. Many are too small to make out clearly by eye, which is why the Forest Service and BLM put a 10x magnifying lens on their basic gear list.

Does gold float?

Gold is about 19 times as heavy as water, so a solid piece sinks fast. Flour gold is different because each speck is so thin and flat. If the speck stays dry on top, it can sit on the surface of the water instead of sinking.

Panners have known this a long time. A USGS report quotes an account from 1889 on the Snake River: once the black sand had been taken out with a magnet, the fine gold floated while the gray sand sank.

The fix is simple. Make sure every grain in the pan is fully wet and has sunk before you start washing off the top. The same USGS report adds a single drop of detergent to the water for this, which helps the water wet the grains so they sink. At the creek, one drop of dish soap in your pan does the same job.

Where does flour gold collect?

On the gravel bars. The Forest Service and BLM point to the upstream ends of gravel bars, and the bars on the inside of bends, as places where flour gold gathers in a thin layer near the surface. Spring runoff tends to refresh these spots every year, so they are worth checking after high water drops.

How do you keep flour gold in your pan?

1. Screen your material. Run it through a classifier so you are panning grains of a similar size. California's state geologists say material of an even size gives the best recovery in a pan.
2. Wet everything. Let the material soak fully under water, and add one drop of dish soap if you see specks floating.
3. Slow down at the end. Use gentle swirls once you are near the black sand. Pan in calm water, or in a tub at home.
4. Work over a catch pan. Do your final panning over a second pan or tub so anything that slips over the edge can be panned again.
5. Clear the magnetite. Pass a magnet over the wet black sand to lift the magnetite out. With less dark sand covering it, flour gold is much easier to see. Keep the magnet away from steel tools, phones and cards, and read our magnet safety warnings.
6. Check what the magnet lifts. A tiny speck can ride along stuck to a magnetite grain, so drop the magnetic sand into a pan of water and look it over before you toss it.
7. Finish with a quick final pan. Swirl the last of it into a crescent and look for the gold.

Our fine gold recovery guide goes further, with sluice settings, pan surfaces and what larger equipment does. For the magnet step itself, see how to separate gold from black sand. A black sand magnet is the tool for that part.

How do you pick up flour gold?

Usually not with tweezers, because the specks are too small. A snuffer bottle can suck them up from a little water, or you can touch them with a dry fingertip and rinse them into a vial of water.

Is flour gold worth anything?

Yes, but only in quantity. At about 40,000 specks to the troy ounce, any single speck is worth very little. It only adds up when you save a lot of it, and gold is gold no matter how small. We do not quote prices here, because the price of gold changes daily.

Why does flour gold get lost so easily?

Because every gravity method struggles with it. Pans, sluices and other equipment all catch gold by weight, and the finest gold has so little weight that water can carry it off. A California state guide to placer recovery groups flour gold with other very fine gold as the gold that gravity methods tend to lose. Careful panning, as above, is how you keep more of it.