Fluoro-tremolite is a fluorine-dominant member of the amphibole group, forming elongated prismatic or fibrous crystals. It is most frequently encountered in contact metamorphosed limestones and dolomites, often occurring as white to pale green sprays.
Is this fluoro-tremolite?
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 fluoro-tremolite with a known reference. Fluoro-tremolite 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. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed, prismatic, fibrous.
Often confused with
Fluoro-tremolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fluoro-tremolite leaves gray, Actinolite leaves white.
How to tell apart: Streak differs, so Fluoro-tremolite leaves gray, Tremolite leaves white.
How to tell apart: Streak differs, so Fluoro-tremolite leaves gray, Wollastonite leaves white.
Often found alongside fluoro-tremolite
Minerals reported to co-occur with fluoro-tremolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- □Ca₂Mg₅Si₈O₂₂F₂
- Mohs hardness
- 5-6
- Density
- 3.044 g/cm³
- Colors
- Streak
- Gray
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed, prismatic, fibrous
- Cleavage
- Perfect on {110}, with intersections at ~56° and ~124°; partings on {100} and {001}
- Rarity
- Uncommon
- Uses
- Collector, Mineralogical study
- Host rock
- A rock-forming mineral in skarn (Sparta, New Jersey)
Where rockhounds find fluoro-tremolite
Classic worldwide localities
- Limecrest-Southdown quarry, Sparta, New Jersey, USA
Field-hunting tip
Where it forms: A rock-forming mineral in skarn (Sparta, New Jersey). If you start seeing calcite, chondrodite, pyrrhotite in float, you are in the right ground. Typical habit: bladed, prismatic, fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluoro-tremolite?+
Where is fluoro-tremolite found?+
Is fluoro-tremolite safe to handle?+
What rocks look like fluoro-tremolite?+
What minerals are found with fluoro-tremolite?+
What kind of rock does fluoro-tremolite form in?+
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Find fluoro-tremolite on the map
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