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Classifier Mesh Sizes

Classifiers are used to size material accurately for classification – often used by gold prospectors who need to size concentrate for use in spiral wheels or the like.

  • 1/2 inch (the largest screen) is about 4 holes per square inch (use to remove worthless larger rocks)
  • 1/4 inch is about 16 holes per square inch (use to reduce size of gravel material for easier sluicing or panning)
  •  1/8 inch is about 64 holes per square inch (use for final clean up of gold concentrates from black sand or for recovery of small gem stones)
  •  1/12 inch mesh – good all around size.
  •  1/20 inch – FINE MESH is about equal to window screen (use for final clean up of FINER gold from your black sand or for recovery of very small garnets and gemstones, etc…)
  •  1/30 inch  – SUPER FINE MESH – a very tight weave
  •  1/50 inch – VERY FINE MESH – 2500 holes per square inch- OFTEN USED WITH #30 and #70 screen for BLUE BOWL CLEANUP
  •  1/70 inch – VERY FINE MESH – 4900 holes per square inch – use with the #6 (1/30″) and #7 (1/50″) screens for best blue bowl recovery.
  •  1/100 inch – the smallest screen – use for microscopic gold recovery and ultra fine gold dust and flakes.

Note that the standard pair of gemstone sieves will almost always be 1/4″ and 1/8″ – you can quickly go through the larger material on the top sieve and then anything that goes through the bottom sieve will usually be too small to worry about.

See the photo gallery below to get a feel for what these mesh sizes look like in reference to a metric/inch ruler.