Graeserite is an exceptionally rare arsenic-iron-titanium oxide mineral known primarily from the Binntal region of Switzerland. It typically appears as tiny, black, tabular crystals embedded within mineral-rich pockets of metamorphic dolomitic marble. Due to its scarcity and complex chemistry, it is a highly sought-after prize for advanced mineralogists and systematic collectors.
Is this graeserite?
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 graeserite with a known reference. Graeserite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, aggregates, radial.
Often confused with
Graeserite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside graeserite
Minerals reported to co-occur with graeserite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₄Ti₃AsO₁₃(OH)
- Mohs hardness
- 5.5
- Density
- 4.62 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, aggregates, radial
- Cleavage
- Moderate on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In hydrothermal Alpine-type fissures (Switzerland)
Where rockhounds find graeserite
Classic worldwide localities
- Monte Leone Nappe, Binntal Region, Western Alps, Switzerland (TL)
- Monte Arsiccio mine, Apuan Alps, Tuscany, Italy
Field-hunting tip
Where it forms: In hydrothermal Alpine-type fissures (Switzerland). If you start seeing anatase, arsenopyrite, asbecasite in float, you are in the right ground. Typical habit: acicular, aggregates, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify graeserite?+
Where is graeserite found?+
Is graeserite safe to handle?+
What rocks look like graeserite?+
What minerals are found with graeserite?+
What kind of rock does graeserite form in?+
What is graeserite used for?+
Find graeserite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
