Kaersutite is a titanium-rich amphibole typically found as short, prismatic, dark-colored crystals in alkaline volcanic or plutonic rocks. It is most easily identified by its distinctive dark brown color and classic amphibole cleavage, though it is often difficult to distinguish from other dark members of the amphibole group without chemical analysis.
Is this kaersutite?
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 kaersutite with a known reference. Kaersutite 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: brownish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Kaersutite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside kaersutite
Minerals reported to co-occur with kaersutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂(Mg₃AlTi)(Si₆Al₂)O₂₂O₂
- Mohs hardness
- 5-6
- Density
- 3.2-3.28 g/cm³
- Colors
- Streak
- Brownish gray
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- Perfect on {110}, intersecting at 56° and 124°; partings on {100}, {001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Common as phenocrysts in alkalic volcanic rocks; in gabbroic and peridotitic nodules in alkalic basalts; in syenites, monzonites, carbonatite tuffs, and alkalic gabbros
Where rockhounds find kaersutite
Classic worldwide localities
- Boulder Dam, Mohave Co., and near San Carlos, Gila Co., Arizona, USA
- Linosa, Pelagian Islands, south of Sicily, Italy
- Mont Saint-Hilaire, Quebec, Canada
- Chikaishi, Oki Island, Shimane Prefecture, and at Mushozu and Numazu, Iki Island, Nagasaki Prefecture, Japan
- Kakanui, New Zealand
Field-hunting tip
Where it forms: Common as phenocrysts in alkalic volcanic rocks; in gabbroic and peridotitic nodules in alkalic basalts; in syenites, monzonites, carbonatite tuffs, and alkalic gabbros. If you start seeing titanian augite, rhönite, olivine in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kaersutite?+
Where is kaersutite found?+
What rocks look like kaersutite?+
What minerals are found with kaersutite?+
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What is kaersutite used for?+
Find kaersutite on the map
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