Guidottiite is a rare manganese-dominant member of the serpentine subgroup. It typically forms microscopic platy or fibrous layers in hydrothermal veins associated with manganese deposits, often requiring analytical methods for definitive identification.
Is this guidottiite?
4-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 guidottiite with a known reference. Guidottiite sits at Mohs 4.25, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous to silky.
- 3Match the color rangeCompare against the expected color range: black.
- 4Look at form & habitCrystal system: hexagonal. Typical habit: platy or fibrous aggregates.
Often confused with
Guidottiite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Guidottiite is noticeably harder (Mohs 4.25 vs. 2.5); luster reads vitreous to silky on Guidottiite and silky on Chrysotile.
How to tell apart: Guidottiite is noticeably harder (Mohs 4.25 vs. 2.5); luster reads vitreous to silky on Guidottiite and waxy on Lizardite.
How to tell apart: Guidottiite is noticeably harder (Mohs 4.25 vs. 2.5-3.5); luster reads vitreous to silky on Guidottiite and resinous, greasy, silky, waxy, earthy on Antigorite.
Often found alongside guidottiite
Minerals reported to co-occur with guidottiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₂Fe(SiFe)O₅(OH)₄
- Mohs hardness
- 4.25
- Density
- 3.33 g/cm³
- Colors
- Luster
- Vitreous to silky
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Platy or fibrous aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a pocket in a hydrothermally altered, bedded manganese deposit
Where rockhounds find guidottiite
Classic worldwide localities
- N’chwaning 2 mine, Kalahari manganese field, Republic of South Africa
Field-hunting tip
Where it forms: In a pocket in a hydrothermally altered, bedded manganese deposit. If you start seeing hematite, chlorite, leucophoenicite in float, you are in the right ground. Typical habit: platy or fibrous aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find guidottiite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
