Gold in Dartmoor A research project

The principle

Gold has a specific gravity of about 19. Quartz sand is about 2.65. Water is 1. That difference is the entire technology. If you agitate a mixture of sand, gravel and gold under water and let it settle, the gold goes to the bottom every time, without exception, and stays there while you wash the lighter material away over the lip of the pan.

Everything that goes wrong in panning is one of two errors: not letting the gold settle before you tip, or tipping too steeply. Both are cured by slowing down.

The kit

You need remarkably little.

Essential

  • A pan. 14 inch (35 cm) plastic, green or black, with riffles moulded into one side. Plastic beats steel: lighter, does not rust, and its slight static grip on fine gold is a genuine advantage. Green shows up gold better than black for most eyes.
  • A classifier sieve that sits on the pan, 1/2 inch and 1/8 inch mesh. Screening out the big stuff before you pan doubles your speed.
  • A garden trowel or small spade, and a bucket.
  • A crevice tool: a flattened screwdriver or a proper crevicing pick for cleaning out bedrock cracks.
  • A snuffer bottle (a squeeze bottle with a narrow tube) and small vials to keep what you find.
  • Wellingtons or waders, and gloves. Dartmoor water is cold in August and painful in February.

Useful

  • A hand lens (10×), see the identification page.
  • A small magnet for pulling black sand out of your concentrate.
  • A tarpaulin, so you can dig without smearing spoil across a field.

Leave at home

  • Sluices, highbankers, dredges, pumps. Mechanised working takes you out of “recreational panning” and into activity that engages Environment Agency consents and will make landowners refuse you. It is also completely unnecessary for assessing whether a stream carries gold.

Where to sample

This is the part that separates a productive day from a wasted one. Gold moves downstream in floods, then stops the instant the current slackens. Sample where the current slackens.

Where gold collects in a stream A schematic plan view of a meandering stream showing gold accumulating on the inside of bends, behind boulders, at the head of gravel bars, in bedrock cracks and at sudden widenings where the current slows. flow Bedrock cracks clean them out Inside of the bend head of the gravel bar Downstream of a boulder Sudden widening current drops, gold drops gold and other heavy minerals
Gold is about nineteen times denser than water and roughly seven times denser than the quartz sand around it. Everywhere the current slows, it stops moving before anything else does, and stays there.

In priority order:

  1. Bedrock crevices. If bedrock is exposed in the stream bed, the cracks in it are a natural sluice that has been running for ten thousand years. Clean them out with a crevice tool, right down to the bottom of the crack. This is the highest-value sampling you can do.
  2. The inside of bends, especially at the upstream end of the gravel bar, where the flow first loses energy.
  3. Immediately downstream of large boulders, in the slack tail.
  4. Where the channel suddenly widens, or where it drops into a plunge pool below a step.
  5. The base of the gravel, always. Gold works its way down through loose gravel until it hits something it cannot pass. The bottom six inches, and the contact with bedrock or with a clay layer, are worth more than everything above them.

The technique

Roughly ten minutes per pan once you are practised. Do not rush; the whole thing hinges on the gold having time to settle.

  1. Fill the pan about two-thirds with screened material. Overfilling is the beginner’s mistake.
  2. Submerge it completely and knead the contents with your fingers, breaking up every clay lump. Clay traps fine gold and floats it out of the pan. Take your time here.
  3. Shake it level, side to side, still fully submerged. Ten or fifteen firm shakes. This is the stratification step: you are letting the gold work down to the bottom. If you do only one thing properly, do this.
  4. Tilt slightly forward and sweep the top layer of light material off the lip with a gentle circular or forward-and-back motion, keeping the pan under water.
  5. Level and shake again. Every few sweeps, bring it back flat and re-stratify. The gold must be given repeated chances to sink.
  6. Repeat until you are down to a tablespoon or two of dark concentrate, mostly magnetite and other heavy black sand.
  7. Finish carefully. Little water in the pan now, tilted, with a slow swirl that fans the black sand out in a tail. Gold, being heaviest, sits at the back of the tail. On Dartmoor-area streams expect a lot of black sand and, given the tin history, quite possibly cassiterite, a dense, dark, resinous-brown tin oxide that behaves very like gold in a pan and is itself a good sign you are in the right ground.
  8. Lift what you find with a snuffer bottle. Not with wet fingers; fine flakes go everywhere.

Working responsibly

This matters more than the gold, and it is the difference between a landowner who lets you back and one who does not.

  • Never dig the banks. Bank digging causes erosion and risks offences relating to otters, water voles and kingfishers. The British Gold Panning Association code prohibits it outright.
  • Work loose material in the stream bed, not consolidated banks or vegetation.
  • Fill in every hole before you move on, and re-level disturbed gravel.
  • Never work spawning gravels in the salmonid season. Devon rivers carry salmon and sea trout, and a redd looks exactly like a promising gravel bar.
  • One small site at a time. Do not leave a trail of pits along half a mile of stream.
  • Take out everything you brought in, obviously.
  • Do not pan below a farmyard or a road drain unless you enjoy sorting your concentrate for lead shot, brass fragments and slag. BGS specifically flagged basic-slag fertiliser contamination in south Devon drainage Leake 1988.

Realistic expectations

A competent panner on a favourable South Hams tributary with permission might see a handful of flakes over a full day. Devon gold is fine and often dendritic rather than nuggety Leake 1990. You are looking for specks a millimetre or less across.

If you want a bulk assessment of a stream rather than an afternoon’s fun, the method BGS used is worth copying: pan a fixed volume from many sites rather than a large volume from one. Prospecting is a mapping exercise. The pan is just how you read the map.