Thortveitite is a rare mineral consisting of scandium yttrium silicate (Sc,Y)2Si2O7. It is the most widespread scandium mineral,<ref>Template:Mindat</ref> but natural thortveitite is not widely exploited as a source of scandium metal. Most scandium is derived from mine tailings, which can include thortveitite.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Thortveitite mining in the United States ceased in 1969.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, a Norwegian engineer. It is grayish-green, black or gray in color.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref>
A transparent gem quality example was found in 2004, and reported in The Journal of Gemmology.<ref>Template:Cite journal</ref>