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 — Almeidaite leaves dark brown, Crichtonite leaves black.
How to tell apart: Streak differs — Almeidaite leaves dark brown, Lindsleyite leaves black.
How to tell apart: Streak differs — 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 — that is 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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