Potassic-fluoro-hastingsite is a rare member of the amphibole supergroup, specifically within the hastingsite group. It typically appears as dark, prismatic to massive crystals in alkaline igneous environments and is primarily identified via chemical analysis due to its striking similarity to other common hornblende-group minerals.
Is this potassic-fluoro-hastingsite?
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-fluoro-hastingsite with a known reference. Potassic-fluoro-hastingsite 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-fluoro-hastingsite leaves a white to pale gray streak.
- 3Read the lusterHold the specimen under a strong light. Potassic-fluoro-hastingsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, brownish black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Potassic-fluoro-hastingsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Potassic-fluoro-hastingsite leaves white to pale gray, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Potassic-fluoro-hastingsite leaves white to pale gray, Hastingsite leaves white to light gray.
Often found alongside potassic-fluoro-hastingsite
Minerals reported to co-occur with potassic-fluoro-hastingsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂(Fe₄Fe)Si₆Al₂O₂₂(F,OH)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.5 g/cm³
- Streak
- White to Pale Gray
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- Perfect in Two Directions
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Syenites
- Typical price
- $15-80 per specimen
Where rockhounds find potassic-fluoro-hastingsite
Classic worldwide localities
- Norway
- Canada
- USA
Field-hunting tip
Look in alkaline igneous rocks, syenites country — that is the host setting where potassic-fluoro-hastingsite typically forms. If you start seeing nepheline, feldspar, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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