Standard MSHA rock dust specifications:

• Pulverized limestone, dolomite, gypsum, anhydrite, shale, adobe, or other inert material, preferably light colored"
• 100% passing #20 mesh screen
• 70% passing #200 mesh screen
• Wetted and dried particles will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air;
• Less than 5% combustible matter-Dillon guarantees 0% combustible matter.
• Less than 4% free and combined silica (SiO2)-Dillon guarantees average not to exceed 2.0%.

Typical EDC analysis:

#20 mesh screen	100%
#200 mesh screen	85.5%
Caking	non-caking
Combustible	non-combustible
Silica	less than 2%