About: http://webisa.webdatacommons.org/370732546

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	However, they do tend to occur - as types of minerals, rather than metals - in relatively low concentrations, rather than as a rich ore which could be more economically be extracted from the earth.
http://www.w3.org/ns/prov#wasQuotedFrom	telegraph.co.uk