Ferro-tschermakite is an iron-rich member of the amphibole supergroup, commonly found in metamorphic environments like amphibolites and schists. It typically appears as dark, prismatic, or acicular crystals that can be challenging to distinguish from other dark hornblende-group members without chemical analysis.
Is this ferro-tschermakite?
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 ferro-tschermakite with a known reference. Ferro-tschermakite 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. Ferro-tschermakite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Ferro-tschermakite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Ferro-tschermakite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ferro-tschermakite leaves pale green, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Ferro-tschermakite leaves pale green, Tschermakite leaves white.
How to tell apart: Streak differs — Ferro-tschermakite leaves pale green, Actinolite leaves white; luster reads vitreous on Ferro-tschermakite and vitreous to silky on Actinolite.
Often found alongside ferro-tschermakite
Minerals reported to co-occur with ferro-tschermakite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- □Ca₂(Fe²⁺₃Al₂)(Si₆Al₂)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.4-3.5 g/cm³
- Colors
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect Prismatic
- Rarity
- Uncommon
- Uses
- Collector, Petrological Research
- Host rock
- Metamorphic Rocks
- Typical price
- $20-100 per specimen
Where rockhounds find ferro-tschermakite
Classic worldwide localities
- Scotland
- Norway
- USA
- Russia
Field-hunting tip
Look in metamorphic rocks country — that is the host setting where ferro-tschermakite typically forms. If you start seeing quartz, plagioclase, biotite 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 ferro-tschermakite on the map
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