Katophorite is a rare member of the sodic-calcic amphibole group typically found in alkaline igneous environments. It is identified by its dark, elongated prismatic crystals and distinct pleochroism, which can be challenging to distinguish from other dark amphiboles without chemical analysis.
Is this katophorite?
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 katophorite with a known reference. Katophorite 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: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, dark greenish black, bluish black, reddish yellow, bluish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: epitaxial, granular, prismatic.
Often confused with
Katophorite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside katophorite
Minerals reported to co-occur with katophorite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaNaCa(Mg₄Al)(Si₇Al)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.2-3.5 g/cm³
- Colors
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Epitaxial, granular, prismatic
- Cleavage
- Perfect on {110}, intersecting at ~56° and ~124°; parting on {010}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In alkalic volcanic and plutonic igneous rocks; in blueschist facies jadeitites
Where rockhounds find katophorite
Classic worldwide localities
- May occur in the Oslo (Christiania) district, Norway, from where it was originally described
- Rallier-du-Baty Peninsula, Kerguelen Island, in the south Indian Ocean
- Tawmaw, Kachin State, northern Myanmar (Burma)
Field-hunting tip
Where it forms: In alkalic volcanic and plutonic igneous rocks; in blueschist facies jadeitites. If you start seeing arfvedsonite, aegirine, nepheline in float, you are in the right ground. Typical habit: epitaxial, granular, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify katophorite?+
Where is katophorite found?+
What rocks look like katophorite?+
What minerals are found with katophorite?+
What kind of rock does katophorite form in?+
What is katophorite used for?+
Find katophorite on the map
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