Grattarolaite is a very rare iron-antimony oxide that typically occurs as microscopic reddish-brown crystals or thin coatings. It was first identified in the manganese-rich mines of Liguria, Italy, where it forms in association with other rare mineral species. Collectors prize it for its extreme rarity and distinctive chemical composition.
Is this grattarolaite?
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 grattarolaite with a known reference. Grattarolaite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Grattarolaite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Grattarolaite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: dark red, reddish-brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: microscopic crystals, coatings.
Often confused with
Grattarolaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Grattarolaite leaves yellowish-brown, Iron Ore leaves reddish-brown to black; luster reads adamantine on Grattarolaite and metallic to submetallic on Iron Ore.
How to tell apart: Grattarolaite is noticeably harder (Mohs 6 vs. 4-4.5); streak differs — Grattarolaite leaves yellowish-brown, Bindheimite leaves yellow; luster reads adamantine on Grattarolaite and earthy on Bindheimite.
Often found alongside grattarolaite
Minerals reported to co-occur with grattarolaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₃SbO₆
- Mohs hardness
- 6
- Density
- 4.82 g/cm³
- Colors
- Streak
- Yellowish-brown
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Microscopic Crystals, Coatings
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Manganese-rich Metamorphic Deposits
- Typical price
- $50-300 per thumbnail specimen
Where rockhounds find grattarolaite
Classic worldwide localities
- Cerchiara Mine, Liguria, Italy
Field-hunting tip
Look in manganese-rich metamorphic deposits country — that is the host setting where grattarolaite typically forms. If you start seeing hematite, quartz, braunite in float, you are in the right ground. Field specimens usually show a microscopic crystals, coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find grattarolaite on the map
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