Potassic-magnesio-arfvedsonite is a rare member of the amphibole supergroup, typically found in undersaturated alkaline igneous complexes. It is visually similar to other dark amphiboles and is best distinguished through micro-analysis or its specific paragenetic occurrence in syenitic rocks.
Is this potassic-magnesio-arfvedsonite?
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 potassic-magnesio-arfvedsonite with a known reference. Potassic-magnesio-arfvedsonite 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: gray-green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: greenish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, acicular, massive.
Often confused with
Potassic-magnesio-arfvedsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Potassic-magnesio-arfvedsonite leaves gray-green, Arfvedsonite leaves deep bluish gray, gray-green.
How to tell apart: Streak differs, so Potassic-magnesio-arfvedsonite leaves gray-green, Riebeckite leaves greenish brown.
How to tell apart: Streak differs, so Potassic-magnesio-arfvedsonite leaves gray-green, Hornblende leaves grayish-white.
Often found alongside potassic-magnesio-arfvedsonite
Minerals reported to co-occur with potassic-magnesio-arfvedsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNa₂(Mg₄Fe³⁺)Si₈O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.24 g/cm³
- Colors
- Streak
- Gray-green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, acicular, massive
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In syenitic and granitic dikes the product of strongly peralkaline and potassic magma
Where rockhounds find potassic-magnesio-arfvedsonite
Classic worldwide localities
- Buhovo-Seslavtsi pluton, Bulgaria
Field-hunting tip
Where it forms: In syenitic and granitic dikes the product of strongly peralkaline and potassic magma. If you start seeing quartz, potassium feldspar, aegirine-augite in float, you are in the right ground. Typical habit: prismatic crystals, acicular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify potassic-magnesio-arfvedsonite?+
Where is potassic-magnesio-arfvedsonite found?+
What rocks look like potassic-magnesio-arfvedsonite?+
What minerals are found with potassic-magnesio-arfvedsonite?+
What kind of rock does potassic-magnesio-arfvedsonite form in?+
What is potassic-magnesio-arfvedsonite used for?+
Find potassic-magnesio-arfvedsonite on the map
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