About: http://webisa.webdatacommons.org/416286646

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	So, while hardness is a good indicator, it is probably not the only think you should be using to determine which material is better than another for this purpose.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com