Ferro-katophorite is a rare member of the amphibole supergroup characterized by its dark coloration and monoclinic symmetry. It is typically found in alkaline igneous rocks like nepheline syenites, often forming as prismatic, elongate crystals in complex mineral assemblages.
Is this ferro-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 ferro-katophorite with a known reference. Ferro-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: pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, dark brown, dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Ferro-katophorite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferro-katophorite leaves pale brown, Hornblende leaves grayish-white.
How to tell apart: Streak differs, so Ferro-katophorite leaves pale brown, Arfvedsonite leaves deep bluish gray, gray-green.
How to tell apart: Streak differs, so Ferro-katophorite leaves pale brown, Hastingsite leaves greenish gray.
Often found alongside ferro-katophorite
Minerals reported to co-occur with ferro-katophorite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaNaCa[Fe₄Al](Si₇Al)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.5 g/cm³
- Streak
- Pale brown
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- alkaline igneous rocks
Where rockhounds find ferro-katophorite
Classic worldwide localities
- Kola Peninsula, Russia
- Larvik, Norway
- Magnet Cove, USA
Field-hunting tip
Where it forms: alkaline igneous rocks. If you start seeing nepheline, aegirine, orthoclase 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 ferro-katophorite?+
Where is ferro-katophorite found?+
What rocks look like ferro-katophorite?+
What minerals are found with ferro-katophorite?+
What kind of rock does ferro-katophorite form in?+
What is ferro-katophorite used for?+
Find ferro-katophorite on the map
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