Thortveitite is a rare scandium-rich silicate mineral primarily found in granitic pegmatites. It typically occurs as elongated, gray-green prisms and is highly prized by mineral collectors as the primary industrial source of scandium.
Is this thortveitite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch thortveitite with a known reference. Thortveitite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to subadamantine.
- 4Match the color rangeCompare against the expected color range: grayish green, brown, grayish black, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crystalline, prismatic, radial.
Often confused with
Thortveitite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Thortveitite leaves gray, Beryl leaves white.
How to tell apart: Thortveitite is noticeably harder (Mohs 6-7 vs. 5); streak differs, so Thortveitite leaves gray, Apatite leaves white.
How to tell apart: Streak differs, so Thortveitite leaves gray, Zircon leaves white.
Often found alongside thortveitite
Minerals reported to co-occur with thortveitite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sc₂Si₂O₇
- Mohs hardness
- 6-7
- Density
- 3.27-3.58 g/cm³
- Streak
- Gray
- Luster
- Vitreous to subadamantine
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Crystalline, prismatic, radial
- Cleavage
- Prismatic
- Rarity
- Rare
- Uses
- Collector, Source of scandium
- Host rock
- In granite pegmatite dikes (Norway)
Where rockhounds find thortveitite
Classic worldwide localities
- Crystal Mountain fluorite mine, at Darby, Ravalli Co., Montana, USA
- Iveland, at Saetersdalen, Ljosland, Frøysa, and Tuftane, near Frikstad
- Evje, at Flåt, Landverk, and Rampetrollsinken
- Befanamo, Madagascar
- Kyoto Prefecture, in the Isanago mine, Oro, Nakagun, and at Shoroishi, Kobe, Omiya, Japan
- Shilovo-Koneva massif, Ural Mountains, Russia
Field-hunting tip
Where it forms: In granite pegmatite dikes (Norway). If you start seeing euxenite, biotite, oligoclase in float, you are in the right ground. Typical habit: crystalline, prismatic, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify thortveitite?+
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Is thortveitite safe to handle?+
What rocks look like thortveitite?+
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Find thortveitite on the map
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