About: http://webisa.webdatacommons.org/420124969

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	In addition non-metallic materials such as gravel, sand, crushed rock, glasses or other materials having a specific gravity greater than one (1) may be used.
http://www.w3.org/ns/prov#wasQuotedFrom	google.de