rock dust1
/ˈrɒk dʌst/Chiefly North American Mining
noun
Pulverized rock, especially (in later use) as spread in coal mines in order to reduce the risk of coal-dust explosions.
Origin
Early 19th century; earliest use found in American Magazine. From rock + dust.
rock dust2
/ˈrɒk dʌst/North American Mining
verb
[with object] To subject (a coal mine) to rock dusting.
Origin
Early 20th century; earliest use found in Compressed Air Magazine. From rock + dust.