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These are the individual stainless steel classifier screens for the Gold Cube Golden Rule classifier, the jar-and-ring system for sizing concentrates before final cleanup. Each screen is a 3.5-inch stainless mesh disc that drops into the Golden Rule ring between two jars; you shake, and everything smaller than the mesh falls through to the lower jar. Sixteen mesh sizes are available from #4 down to #400, sold one screen at a time so you can fill in the sizes you are missing or replace a screen that has been mistreated.
Why classify concentrates by size
The "Golden Rule" is Gold Cube founder Mike Pung's shorthand for a simple fact: when everything in the pan is the same size, gold rules. Gold is far denser than the sand and black sand around it, but a large flake of magnetite can still out-weigh a tiny piece of gold. Once your gold concentrates are split into narrow size bands, every particle in a band is roughly the same volume, so weight difference is the only thing left and the gold separates immediately in a pan, a Blue Bowl or a miller table. This is the single biggest improvement most people can make to their fine gold recovery, and it costs nothing but a few minutes of shaking.
Mesh size chart
Mesh number is the count of wire openings per linear inch, so the higher the number, the finer the screen. Nominal openings and the job each screen is best at:
| Mesh | Opening | Suggested use |
|---|---|---|
| #4 | 4.75 mm (0.187") | First pass on raw sluice or Gold Cube cons. Pulls out pebbles, roots and pickers you can see by eye. Also the coarsest screen for checking a pan of crevice material. |
| #6 | 3.35 mm (0.132") | Second scalping pass in gravelly cons. Useful when #4 lets too much small gravel through into the pan stage. |
| #8 | 2.36 mm (0.093") | The usual top screen for cleanup. Anything held here is nugget or picker size and is picked out with tweezers rather than panned. |
| #10 | 2.00 mm (0.079") | Splits large flakes from the #8 fraction. Handy in coarse-gold areas where you get a lot of material between #8 and #12. |
| #12 | 1.70 mm (0.067") | Common upper cut for "flake gold" panning. Material held here pans out in seconds with almost no black sand interference. |
| #14 | 1.40 mm (0.055") | Intermediate step when you want every band narrow. Most people skip #14 and #16 unless they are chasing a specific flake size. |
| #16 | 1.18 mm (0.047") | Same role as #14. Worth having if your ground produces a lot of gold in the 1 to 1.5 mm range. |
| #18 | 1.00 mm (0.039") | The 1 mm line. A good single break between "flake" and "fine" if you only run three or four screens. |
| #20 | 0.85 mm (0.033") | The most common break point between flake gold and fine gold. Material through #20 is where a pan starts to lose gold and a Blue Bowl or miller table earns its keep. |
| #30 | 0.60 mm (0.023") | First "fines" band. Pans cleanly with care, and is the top size a Blue Bowl handles comfortably. |
| #40 | 0.425 mm (0.017") | Mid-fines. Typical band for Blue Bowl or miller table runs of Gold Cube concentrate. |
| #50 | 0.30 mm (0.012") | Roughly the finest gold the eye tracks reliably in a pan. Below this, rely on equipment rather than eyesight. |
| #70 | 0.212 mm (0.008") | Fine flour band. Narrowing #50 to #100 into two steps improves Blue Bowl recovery in heavy black sand. |
| #100 | 0.15 mm (0.006") | Start of true flour gold. Standard bottom screen for most prospectors; whatever passes #100 goes to the bowl or table as a single batch. |
| #200 | 0.075 mm (0.003") | Micron-range gold from beach sand, dredge cons and Gold Cube slick-plate cleanup. Needs a slow Blue Bowl run or a miller table, never a pan. |
| #400 | 0.037 mm (0.0015") | The finest screen in the set. Used to strip everything above 400 mesh before a final miller-table pass, or to check whether your ground produces gold this fine at all. |
Openings follow the standard U.S. sieve series; actual wire diameter varies slightly by mesh. For most cleanup work a set of four or five screens two or three sizes apart (for example #8, #20, #50, #100) does the job. Gold Cube also sells the screens as a 4-screen Clean-up Pack and a 16-screen Pro Pack; buy individual screens here to build your own set or add the in-between sizes later.
How they fit
Each screen is 3.5 inches across and sits inside the Golden Rule ring, which threads onto standard wide-mouth jars. Stack a screen between a jar of dry cons on top and an empty jar below, screw the ring tight, and shake. Swap to the next finer screen and repeat with the material that stayed on top. Because the whole assembly is sealed, nothing blows away and nothing spills, which matters when you are down to the fines. The mesh number is stamped on each screen so a stack stays sorted. Stainless steel will not rust from wet cons or react with anything you might later use for cleanup.
Where these fit in a Gold Cube cleanup
A Gold Cube holds fine gold that most sluices lose, which means your cons come out heavy in fine black sand. The normal sequence is: run the Gold Cube, collect the cons, dry them, run them through the Golden Rule screens, then pan or bowl each size band. If you are classifying raw dirt before it goes into a sluice or pan rather than sizing cons afterward, you want a bucket-size gold classifier instead; see our gold classifiers and sifters collection. The Gold Cube Trommel, Clean-Up Kit and Banjo Pan that round out a full cleanup setup are all in the Gold Cube collection.
Includes
- One Golden Rule classifier screen in the mesh size selected
The Golden Rule ring and jars are sold separately as the Golden Rule Classifier System. Everything else you need for a cleanup, from pans to sluices, is in our gold prospecting equipment collection.
Specifications
- Type: interchangeable classifier screen for the Gold Cube Golden Rule jar system
- Diameter: 3.5" (approx. 89 mm)
- Material: stainless steel mesh, stainless rim
- Mesh sizes available: #4, #6, #8, #10, #12, #14, #16, #18, #20, #30, #40, #50, #70, #100, #200, #400
- Marking: mesh number stamped on each screen
- Quantity: sold individually; 4-screen and 16-screen packs available separately
- Use: dry classification of concentrates for gold cleanup
- Brand: Gold Cube, made in the USA
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