Magnesiochloritoid is a rare member of the chloritoid group found in high-pressure, low-temperature metamorphic environments. It typically appears as dark, tabular or platy crystals embedded within schistose host rocks, often requiring microscopic examination for positive identification.
Is this magnesiochloritoid?
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 magnesiochloritoid with a known reference. Magnesiochloritoid sits at Mohs 6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Magnesiochloritoid leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Magnesiochloritoid typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: dark green, black, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, foliated masses, rosettes.
Often confused with
Magnesiochloritoid vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads pearly on Magnesiochloritoid and vitreous on Ottrélite.
How to tell apart: Magnesiochloritoid is noticeably harder (Mohs 6.5 vs. 2-3).
How to tell apart: Luster reads pearly on Magnesiochloritoid and vitreous to resinous on Staurolite.
Often found alongside magnesiochloritoid
Minerals reported to co-occur with magnesiochloritoid. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgAl₂SiO₅(OH)₂
- Mohs hardness
- 6.5
- Density
- 3.5-3.6 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Foliated Masses, Rosettes
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Rocks
- Typical price
- $20-100 per specimen
Where rockhounds find magnesiochloritoid
Classic worldwide localities
- Greece
- Italy
- Spain
- Japan
Field-hunting tip
Look in metamorphic rocks country — that is the host setting where magnesiochloritoid typically forms. If you start seeing quartz, muscovite, chlorite in float, you are in the right ground. Field specimens usually show a tabular crystals, foliated masses, rosettes habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find magnesiochloritoid on the map
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