Unconsolidated naturally occurring mineral particles resulting from the breakdown of rock or organic matter that are small than 2 millimetres in size.
Source
http://www.search.e-laws.gov.on.ca/en/isysquery/c98f5d31-5d2e-47d2-9c41-a7930ae33eef/16/doc/?search=browseStatutes&context=#hit1