Simplify the following text for a Grade 11 native English-speaking person.
Original: Rock flour , or glacial flour , consists of fine-grained , silt-sized particles of rock , generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size .
Simplified: Rock flour , or glacial flour , consists of clay-sized particles of rock , generated by glacial erosion or by artificial grinding to a similar size .