Riebeckite is an amphibole group mineral typically found in silica-rich alkaline igneous rocks like granite. It often occurs as prismatic crystals or as a fibrous, asbestiform variety known as crocidolite, which can replace other minerals during pseudomorphosis.
Is this 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 riebeckite with a known reference. 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. Riebeckite leaves a blue-gray streak.
- 3Read the lusterHold the specimen under a strong light. Riebeckite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark blue, black, blue-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, fibrous, acicular.
Often confused with
Riebeckite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside riebeckite
Minerals reported to co-occur with riebeckite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.0-3.5 g/cm³
- Colors
- Streak
- Blue-gray
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Fibrous, Acicular
- Cleavage
- Perfect Prismatic
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Alkaline Igneous Rocks, Granites, Syenites
- Typical price
- $10-100 per specimen
Where rockhounds find riebeckite
1 mapped spotsClassic worldwide localities
- Quebec, Canada
- South Africa
- Norway
- Scotland
- USA
Field-hunting tip
Look in alkaline igneous rocks, granites, syenites country — that is the host setting where riebeckite typically forms. If you start seeing quartz, albite, aegirine in float, you are in the right ground. Field specimens usually show a prismatic crystals, fibrous, acicular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah — start trip planning there.
Common questions
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Find riebeckite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
