Potassic-pargasite is a rare member of the amphibole supergroup, distinguished by its high potassium content. Collectors typically find it in contact metamorphic zones, specifically in skarns where it forms deep green, well-defined prismatic crystals.
Is this potassic-pargasite?
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-pargasite with a known reference. Potassic-pargasite 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. Potassic-pargasite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Potassic-pargasite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green, black, brownish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, anhedral grains.
Often confused with
Potassic-pargasite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Potassic-pargasite leaves white, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Potassic-pargasite leaves white, Magnesio-hastingsite leaves grayish white.
Often found alongside potassic-pargasite
Minerals reported to co-occur with potassic-pargasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCa₂Mg₄Al(Si₆Al₂)O₂₂(OH,F)₂
- Mohs hardness
- 5-6
- Density
- 3.1-3.3 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Anhedral Grains
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Limestones, Skarns
- Typical price
- $20-150 per specimen
Where rockhounds find potassic-pargasite
Classic worldwide localities
- Pargas, Finland
- Grenville Province, Canada
- Adirondack Mountains, USA
Field-hunting tip
Look in metamorphic limestones, skarns country — that is the host setting where potassic-pargasite typically forms. If you start seeing calcite, diopside, phlogopite in float, you are in the right ground. Field specimens usually show a prismatic crystals, anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find potassic-pargasite on the map
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