Fluoro-riebeckite is an alkaline amphibole often found as deep blue, fibrous, or prismatic crystals. It is typically associated with silica-rich, alkaline igneous environments and is chemically distinguished from standard riebeckite by its high fluorine content.
Is this fluoro-riebeckite?
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 fluoro-riebeckite with a known reference. Fluoro-riebeckite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: blue-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue, dark blue, blue-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, fibrous, asbestos-like, massive.
Often confused with
Fluoro-riebeckite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fluoro-riebeckite leaves blue-gray, Riebeckite leaves greenish brown.
How to tell apart: Streak differs, so Fluoro-riebeckite leaves blue-gray, Arfvedsonite leaves deep bluish gray, gray-green.
Often found alongside fluoro-riebeckite
Minerals reported to co-occur with fluoro-riebeckite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂F₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.4 g/cm³
- Colors
- Streak
- Blue-gray
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, fibrous, asbestos-like, massive
- Cleavage
- Perfect prismatic
- Rarity
- Uncommon
- Uses
- Collector, Scientific study
- Host rock
- alkaline igneous rocks, granites, syenites
Where rockhounds find fluoro-riebeckite
Classic worldwide localities
- Norway
- USA
- Russia
- Madagascar
Field-hunting tip
Where it forms: alkaline igneous rocks, granites, syenites. If you start seeing quartz, albite, aegirine in float, you are in the right ground. Typical habit: prismatic, fibrous, asbestos-like, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluoro-riebeckite?+
Where is fluoro-riebeckite found?+
Is fluoro-riebeckite safe to handle?+
What rocks look like fluoro-riebeckite?+
What minerals are found with fluoro-riebeckite?+
What kind of rock does fluoro-riebeckite form in?+
What is fluoro-riebeckite used for?+
Find fluoro-riebeckite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
