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Basically, grit, mesh, and micron are three different ways to measure particle size. For lapidaries, this is important because particle size defines the coarseness of gem cutting abrasives, such as polishes, cutting compounds, and laps.
By Jeff R. Graham 2 minute read
Gem Cutting Abrasives

Diamond compounds, micron diamond powder, and felt bobs. Photo by cpxmn. Licensed under CC By-SA 2.0.

What Do Grit, Mesh, and Micron Mean?

Grit refers to the size of particles embedded in an abrasive material. The higher the grit, the finer the abrasive. There are different standards for grit used internationally and by manufacturers. For example, just because a polish or compound is labeled as 14,000 grit doesn’t mean that all its content is that size. It depends on the methods used to make and grade the compound. Some manufacturers use an average particle size and some use a “nothing larger than” standard, and so on. Read the label or ask the retailer if you’re not sure of the standard used.

Mesh refers to the number of evenly spaced holes in a screen per square inch. This refers to a traditional technique used to winnow material through a series of screens with increasingly finer mesh sizes. Particles stopped by a screen of a particular mesh were measured by that mesh number.

A micron is a unit (one 10-6 of a meter) used to measure the size of particles in an abrasive material.

Shopping Advice for Gem Cutting Abrasives

In the United States, most diamond compounds or powders are sold in grit sizes (50,000, 100,000, etc). Aluminum oxide and cerium oxide are usually measured in microns.

In general, the more expensive brands of gem cutting abrasives have better quality control for the sizing and grading of their polishes and compounds. You get what you pay for. Beware of very inexpensive abrasives. They’re usually not graded well. It only takes one piece of grit the wrong size to scratch your gemstone and cause problems.

Grit, Mesh, and Micron Conversion Chart

Some of the grits described in the chart below are not commonly available in gem cutting abrasives for various reasons. Nonetheless, they’re shown here for conversion purposes. For example, 60,000 grit is the conversion for 0.5 microns, but you’ll almost never find it available. 50,000 grit is commonly used.

Grit (American Standard) Mesh Micron  Comments
100,000 0-0.5 0.25 Very fine and not used often commercially. Mainly for contest cutting or hobby cutters. Seldom needed.
60,000 0-1 0.5 Seldom used. 50,000 grit is more common and used for polishing sapphire and other hard materials.
14,000 0-2 1 This is the standard commercial polish for sapphire, although I recommend going another step to 50,000.
13,000 1-2 1.5 Seldom used because it’s so close to 14,000.
9,000 2-3 2.5 Seldom used because it’s so close to 8,000.
8,000 2-4 3 This is my standard pre-polish for sapphire and other hard materials.
5,000 2-6 4 Seldom used.
4,500 4-6 5 Seldom used.
2,800 5-10 7 Seldom used. 3,000 is commonly used.
1,800 6-12 9 Seldom used.
1,400 8-20 14 Seldom used.
1,200 10-20 15 Seldom used.
1,050 12-25 18 Seldom used.
800 20-30 25 Seldom used.
600 20-40 30 Commonly used for charging copper laps. I prefer plated laps.
500 30-40 35 Seldom used.
325 40-50 45 Commonly used for charging copper laps. I prefer plated laps.
285 50-60 55 Seldom used.
240 60-80 70 Seldom used. 260 is commonly used for charging copper laps. I prefer plated laps.
225 80-100 90 Commonly used for charging copper laps. I prefer plated laps.
160 100-120 110 Seldom used.
100 120-160 150 Commonly used for charging copper laps. I prefer plated laps.