How Does a Sluice Box Work? Setup, Angle and Cleanup
A sluice box lets a creek do the hard work of separating gold from gravel. Learn how riffles and matting trap gold, how to set the right angle and water flow, and how to clean up without losing fines.
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A gold pan is a great tool for testing, but it is slow. A sluice box lets you process many times more material in the same time by letting the creek do the shaking for you. It is the natural next step once you have found a spot worth working with a pan.
The basic idea
A sluice box is a long, open channel set in moving water. You shovel gravel into the top end. Water carries the material down the box, and along the way it passes over riffles, ridges or bars across the floor of the box.
Riffles create small swirling eddies behind them. Light material, such as sand and pebbles, is kept moving by the current and washes out the end. Heavy material, including gold and black sand, drops into the low-pressure zones behind the riffles and stays trapped.
It is the same principle that makes gold collect behind boulders and in bedrock cracks in a creek, just organised into a box.
The parts of a sluice
| Part | What it does |
|---|---|
| Flare or header | The wide entrance that funnels water into the box |
| Riffles | Bars or ridges that create eddies to trap heavy material |
| Matting or carpet | Lines the floor under the riffles and catches fine gold |
| Expanded metal | A diamond-pattern mesh used in some designs to create many small eddies |
| Classifier | A screen used before the sluice to remove large rocks |
Modern hobby sluices are usually aluminium or plastic and come in many lengths. Some have built-in moulded riffles; others use separate riffle trays over matting.
Types of matting
- Miner's moss is a vinyl loop matting that grips fine gold well.
- Ribbed or vortex matting creates small eddies of its own and is easy to clean.
- Carpet (outdoor or "jute-backed") is traditional and cheap but needs careful washing.
Setting up your sluice
Good setup matters more than the brand of sluice you buy.
1. Find the right spot
You need water that is moving steadily but not violently, and deep enough to cover the bottom of the box. A spot just above a small drop works well because it gives you natural flow through the box. Make sure you can stand safely and have somewhere nearby to dig.
2. Set the angle
A common starting point is a drop of about 2.5 centimetres per 30 centimetres of length, roughly one inch per foot. That is only a guide. Watch how the box behaves:
- Too steep: the riffles look scoured bare, and material races through. You will lose gold.
- Too flat: gravel piles up behind the riffles and they "pack". Gold can no longer drop into the eddies.
You want the riffles to stay partly visible, with a light layer of material moving and gently churning behind them.
3. Adjust the water flow
Water should cover the riffles by a few centimetres and run evenly across the whole width. Stack rocks at the entrance to direct more water into the box or move it slightly sideways to reduce flow.
4. Anchor it
Put a flat rock on the top end or across the middle so the box does not shift or float away. Make sure the box is level from side to side so material spreads evenly.
Feeding the sluice
- Classify first. Running material through a screen into a bucket removes large stones that can block the riffles and push gold out.
- Feed slowly and evenly. Dump a small amount at the top, let it work through, then add more. Shovelling in big loads overloads the riffles.
- Break up clay. Clay balls roll through a sluice and carry gold with them. Soak and break clay in a bucket before feeding.
- Watch the riffles. If they start packing, slow down or adjust the angle.
Cleaning up
How often you clean up depends on the material. Many people do it every few hours or at the end of the day.
- Lift the box slowly and level straight up out of the water, so nothing washes out.
- Place it over a large tub or bucket.
- Remove the riffle tray and rinse it into the tub.
- Roll up the matting carefully and rinse it thoroughly, flexing it under water to release fine gold.
- Pan the concentrates. Work them down using the technique in our panning guide, or save them to process at home.
How much gold does a sluice catch?
A well-set sluice catches most of the coarse gold and a good share of the fine gold. Very fine "flour" gold is harder to keep, especially if the water is too fast. That is why it is worth testing your tailings occasionally with a pan. If you find gold there, adjust the angle or flow.
Sluice vs other methods
A sluice is the classic middle ground between a pan and motorised equipment. If you want to process even more material or work away from the water's edge, a highbanker adds a pump and hopper. In dry country, a dry washer uses air instead of water.
Rules and respect
Many places allow sluice boxes, but not all. British Columbia's recreational panning reserves, for example, allow only a pan and shovel. Some streams are closed during fish spawning. Always check the local rules, avoid digging into banks, fill your holes and leave the creek as you found it.