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, 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.
