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. Kaersutite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kaersutite typically shows a vitreous luster.
- 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
- NaCa₂Mg₃Ti(Si₆Al₂)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.2-3.3 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect Prismatic
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks
- Typical price
- $10-50 per specimen
Where rockhounds find kaersutite
Classic worldwide localities
- Kaersut, Greenland
- Mt. Erebus, Antarctica
- Boulder Dam, Arizona, USA
- Eifel, Germany
- Pantelleria, Italy
Field-hunting tip
Look in alkaline igneous rocks country — that is the host setting where kaersutite typically forms. If you start seeing titanite, magnetite, plagioclase in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find kaersutite on the map
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