About: http://webisa.webdatacommons.org/273333165

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	These materials are usually mined out of the earth and therefore regularly have earth, clay, shale, sand and other minerals mixed into their quantities.
http://www.w3.org/ns/prov#wasQuotedFrom	google.fr