Thortveitite
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Thortveitite is a rare mineral consisting of scandium yttrium silicate (Sc, Y)₂Si₂O₇. It is the primary source of scandium. Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, a Norwegian engineer. It is grayish-green, black... Wikipedia
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal system: Monoclinic
Mohs scale hardness: 5–6
Space group: C2/m
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