Demagistrisite is an exceptionally rare member of the garnet group discovered in the manganese mines of the Aosta Valley. It typically occurs as small, dark, anhedral grains embedded within manganese-rich silicate rocks and is primarily of interest to advanced mineralogists and systematic collectors.
Is this demagistrisite?
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 demagistrisite with a known reference. Demagistrisite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Demagistrisite leaves a beige streak.
- 3Read the lusterHold the specimen under a strong light. Demagistrisite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: anhedral grains.
Often confused with
Demagistrisite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Spessartine is the harder of the two (Mohs 6.5-7.5 vs. 3.5); streak differs, so Demagistrisite leaves beige, Spessartine leaves white.
How to tell apart: Braunite is the harder of the two (Mohs 6-6.5 vs. 3.5); streak differs, so Demagistrisite leaves beige, Braunite leaves black; luster reads vitreous on Demagistrisite and submetallic on Braunite.
Often found alongside demagistrisite
Minerals reported to co-occur with demagistrisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaCa₂Mn³⁺₄(Si₃O₁₀)(Si₂O₇)(OH)₄·3H₂O
- Mohs hardness
- 3.5
- Density
- 3.52 g/cm³
- Colors
- Streak
- Beige
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Anhedral Grains
- Cleavage
- Good On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Manganese-rich Rocks
Where rockhounds find demagistrisite
Classic worldwide localities
- St. Marcel, Aosta Valley, Italy
Field-hunting tip
Look in metamorphic manganese-rich rocks country, the host setting where demagistrisite typically forms. If you start seeing braunite, quartz, hematite in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find demagistrisite on the map
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