About: http://webisa.webdatacommons.org/271774683

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	Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red, or other tint.Following is a list of contaminating elements and related color hues:
http://www.w3.org/ns/prov#wasQuotedFrom	worthpoint.com