Potassic-sadanagaite is a rare member of the complex calcic-amphibole group, typically identified by its dark, iron-rich prismatic crystals. It is most often discovered in high-grade metamorphic skarns where it forms through the interaction of aluminous-rich fluids with carbonate host rocks.
Is this potassic-sadanagaite?
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-sadanagaite with a known reference. Potassic-sadanagaite 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-sadanagaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Potassic-sadanagaite typically shows a vitreous luster.
- 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
Potassic-sadanagaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Potassic-sadanagaite leaves white, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Potassic-sadanagaite leaves white, Hastingsite leaves white to light gray.
Often found alongside potassic-sadanagaite
Minerals reported to co-occur with potassic-sadanagaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na)Ca₂(Fe²⁺₃Al₂)(Si₅Al₃)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.4-3.5 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Skarns and Limestone Contact Zones
- Typical price
- $50-300 per specimen
Where rockhounds find potassic-sadanagaite
Classic worldwide localities
- Japan
- Canada
- USA
Field-hunting tip
Look in metamorphic skarns and limestone contact zones country — that is the host setting where potassic-sadanagaite typically forms. If you start seeing calcite, diopside, spinel in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find potassic-sadanagaite on the map
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