Almeidaite is a rare lead-zinc-manganese titanate belonging to the crichtonite group. It is typically found as small, dark, tabular crystals within carbonatite complexes, most notably from the Jacupiranga mine in Brazil.
Is this almeidaite?
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 almeidaite with a known reference. Almeidaite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Almeidaite leaves a dark brown streak.
- 3Read the lusterHold the specimen under a strong light. Almeidaite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular rhombohedral crystals.
Often confused with
Almeidaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Almeidaite leaves dark brown, Crichtonite leaves black.
How to tell apart: Streak differs, so Almeidaite leaves dark brown, Lindsleyite leaves black.
How to tell apart: Streak differs, so Almeidaite leaves dark brown, Mathiasite leaves brownish black.
Often found alongside almeidaite
Minerals reported to co-occur with almeidaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbZn₂(Mn³⁺,Ti,Fe³⁺,Fe²⁺)₂₁O₃₈
- Mohs hardness
- 5-6
- Density
- 4.8 g/cm³
- Colors
- Streak
- Dark Brown
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular Rhombohedral Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Carbonatite
- Typical price
- $100-500 depending on specimen quality
Where rockhounds find almeidaite
Classic worldwide localities
- Jacupiranga mine, Brazil
Field-hunting tip
Look in carbonatite country, the host setting where almeidaite typically forms. If you start seeing calcite, magnetite, dolomite in float, you are in the right ground. Field specimens usually show a tabular rhombohedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find almeidaite on the map
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