Frankamenite is a rare silicate mineral primarily found in alkaline igneous complexes, occurring most notably in the Murun Massif of Russia. It typically appears as fibrous to acicular prismatic crystals that often exhibit a pale blue to white coloration.
Is this frankamenite?
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 frankamenite with a known reference. Frankamenite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: greenish blue, bluish gray, greenish gray, lilac gray.
- 5Look at form & habitCrystal system: triclinic. Typical habit: lath.
Often confused with
Frankamenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Frankamenite leaves pale blue, Wollastonite leaves white.
How to tell apart: Streak differs, so Frankamenite leaves pale blue, Pectolite leaves white; luster reads vitreous on Frankamenite and silky, subvitreous on Pectolite.
Often found alongside frankamenite
Minerals reported to co-occur with frankamenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₃Na₃Ca₅Si₁₂O₃₀(OH,F)₂·H₂O
- Mohs hardness
- 5.5
- Density
- 2.68 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Lath
- Cleavage
- Good on {010}; good on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Charoitic rocks of the Murun alkaline massif
Where rockhounds find frankamenite
Classic worldwide localities
- Charo and Tokko Rivers, Murun, Murunsky massif, Yakutia, East Siberia, Russia (type locality)
Field-hunting tip
Where it forms: Charoitic rocks of the Murun alkaline massif. If you start seeing kalsilite, potassian feldspar, aegirine in float, you are in the right ground. Typical habit: lath. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify frankamenite?+
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What rocks look like frankamenite?+
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Find frankamenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
