Sadanagaite is a complex amphibole group mineral typically identified by its dark color and prismatic habit within metamorphic environments. It is chemically distinguished by high levels of aluminum and potassium substitution, often requiring analytical methods for definitive field identification. It is most frequently found as an accessory mineral in high-grade metamorphic skarn deposits.
Is this 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 sadanagaite with a known reference. Sadanagaite sits at Mohs ~6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive.
Often confused with
Sadanagaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Sadanagaite leaves very light brown, Hornblende leaves grayish-white.
How to tell apart: Streak differs, so Sadanagaite leaves very light brown, Hastingsite leaves greenish gray.
How to tell apart: Streak differs, so Sadanagaite leaves very light brown, Ferro-edenite leaves white.
Often found alongside sadanagaite
Minerals reported to co-occur with sadanagaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂(Mg₃Al₂)(Si₅Al₃)O₂₂(OH)₂
- Mohs hardness
- ~6
- Density
- 3.3 g/cm³
- Colors
- Streak
- Very light brown
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, massive
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- By contact metamorphism, producing banded skarns, under amphibolite to pyroxene hornfels facies conditions; from eclogites
Where rockhounds find sadanagaite
Classic worldwide localities
- Yuge Island, Ehime Prefecture, and in the Nogo-Hakusan area, Fukui Prefecture, Japan
- Botallack mine, St. Just, Cornwall, England
- Oetztal, Austria
Field-hunting tip
Where it forms: By contact metamorphism, producing banded skarns, under amphibolite to pyroxene hornfels facies conditions; from eclogites. If you start seeing vesuvianite, hercynite, sphene in float, you are in the right ground. Typical habit: prismatic crystals, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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What rocks look like sadanagaite?+
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Find sadanagaite on the map
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