Rasvumite is a rare potassium iron sulfide typically found as dark, metallic, needle-like or prismatic crystals in alkaline pegmatites. It is best known from the Khibiny Massif in Russia, where it occurs within hyper-agpaitic rocks associated with minerals like aegirine and nepheline.
Is this rasvumite?
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 rasvumite with a known reference. Rasvumite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rasvumite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Rasvumite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, acicular, radiating aggregates.
Often confused with
Rasvumite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 3); streak differs, so Rasvumite leaves black, Pyrite leaves greenish-black to brownish-black.
How to tell apart: Streak differs, so Rasvumite leaves black, Chalcopyrite leaves greenish-black.
Often found alongside rasvumite
Minerals reported to co-occur with rasvumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KFe₂S₃
- Mohs hardness
- 3
- Density
- 3.37 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Acicular, Radiating Aggregates
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Pegmatites
- Typical price
- $50-300 per specimen depending on size and association
Where rockhounds find rasvumite
Classic worldwide localities
- Rasvumchorr Mountain, Khibiny Massif, Russia
- Kola Peninsula, Russia
Field-hunting tip
Look in alkaline igneous pegmatites country, the host setting where rasvumite typically forms. If you start seeing aegirine, nepheline, kalsilite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rasvumite?+
Where is rasvumite found?+
How much is rasvumite worth?+
What rocks look like rasvumite?+
What minerals are found with rasvumite?+
What kind of rock does rasvumite form in?+
What is rasvumite used for?+
Find rasvumite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
