Screen Mesh Sizes
As appearing in The Gold Nugget, April 1997
Submitted by Ken Oyler
Last updated: 18 DEC 2004
Mesh refers to the openings between the threads of a screen and is measured by the number of openings per inch; that is, 10 mesh equals 10 holes or openings per inch.
- 10 mesh = 2.000 mm = .0787 in.
- 12 mesh = 1.700 mm = .0661 in.
- 14 mesh = 1.400 mm = .0555 in.
- 20 mesh = 0.850 mm = .0331 in.
- 40 mesh = 0.425 mm = .0165 in.
- 50 mesh = 0.300 mm = .0117 in.
- 60 mesh = 0.250 mm = .0098 in.
- 80 mesh = 0.180 mm = .0070 in.
- 100 mesh = 0.150 mm = .0059 in.
- 120 mesh = 0.125 mm = .0049 in.
![[ GPR members using a highbanker on Clear Creek ]](../images/gpr_screenmesh.jpg)
Grain gold is smaller than a troy grain-sized nugget.
Coarse gold will not pass through a 10-mesh screen.
Medium gold will not pass through a 20-mesh screen and averages about 2,000 colors to a troy ounce.
Fine gold will not pass through a 40-mesh screen and averages about 12,000 colors to a troy ounce.
Very Fine gold passes through a 40-mesh screen and averages about 40,000 colors to a troy ounce. Flour gold is even finer than Very Fine gold. It has such a large surface area in proportion to its weight, it usually cannot break the suface tension of water. It tends to float out of pans and over riffles.
Color simply means a tiny particle of gold.
Troy refers to a system of weights in use for precious metals, such as gold and silver, and gems, in which 12 troy ounces equals one troy pound. Troy weights include pennyweights, ounces, and pounds. The ounces and pounds do not equal the avoirdupois weights system, the customary U.S. system, in which other common goods are measured (16 avoirdupois ounces equals 1 avoirdupois pound). For comparison, one troy ounce equals 1.097 avoirdupois ounce.
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