Ferri-kaersutite is a rare member of the amphibole supergroup characterized by high iron and titanium content. It typically forms dark, prismatic crystals within alkalic volcanic rocks and is often difficult to distinguish from standard kaersutite without chemical analysis.
Is this ferri-kaersutite?
4-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 ferri-kaersutite with a known reference. Ferri-kaersutite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 3Match the color rangeCompare against the expected color range: brown.
- 4Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Ferri-kaersutite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ferri-kaersutite
Minerals reported to co-occur with ferri-kaersutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂ (Mg₃Fe³⁺Ti) (Si₆Al₂) O₂₂O₂
- Mohs hardness
- 5-6
- Density
- 3.190 g/cm³
- Colors
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an ultramafic (spinel-bearing lherzolite) mantle xenolith in alkaline mafic rock
Where rockhounds find ferri-kaersutite
Classic worldwide localities
- Harrow Peaks, Victoria Land, Antarctica
Field-hunting tip
Where it forms: In an ultramafic (spinel-bearing lherzolite) mantle xenolith in alkaline mafic rock. If you start seeing forsterite, diopside, cr-bearing spinel 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 ferri-kaersutite?+
Where is ferri-kaersutite found?+
What rocks look like ferri-kaersutite?+
What minerals are found with ferri-kaersutite?+
What kind of rock does ferri-kaersutite form in?+
What is ferri-kaersutite used for?+
Find ferri-kaersutite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
