Tamarugite is a rare sodium aluminum sulfate mineral typically found as a secondary mineral in arid evaporite settings. Collectors look for its characteristic white to colorless tabular crystals or efflorescent crusts primarily in desert environments like those in Northern Chile.
Is this tamarugite?
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 tamarugite with a known reference. Tamarugite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, prismatic, tabular.
Often confused with
Tamarugite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside tamarugite
Minerals reported to co-occur with tamarugite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAl(SO₄)₂·6H₂O
- Mohs hardness
- ~3
- Density
- 2.06 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, prismatic, tabular
- Cleavage
- {010}, perfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A secondary mineral in oxidized sulfide-bearing alkali-rich aluminous rocks, with sodium supplied from hydrothermal solutions or sea-spray; as efflorescences in active geothermal systems
Where rockhounds find tamarugite
Classic worldwide localities
- Eureka, St. Louis Co., and at Fulton, Calloway Co., Missouri, USA
- Cerro Pintados, 80 km southeast of Iquique, Tarapacá, Chile
- Antofagasta, at the Compania mine, eight km south of Sierra Gorda, Chile
- Alcaparrosa, near Cerritos Bayos, southwest of Calama, Chile
- Chuquicamata, and Quetena, west of Calama, Chile
- Atacama, at Tierra Amarilla, southeast of Copiapó, Chile
Field-hunting tip
Where it forms: A secondary mineral in oxidized sulfide-bearing alkali-rich aluminous rocks, with sodium supplied from hydrothermal solutions or sea-spray; as efflorescences in active geothermal systems. If you start seeing pickeringite, coquimbite, quenstedtite in float, you are in the right ground. Typical habit: massive, prismatic, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tamarugite?+
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What rocks look like tamarugite?+
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Find tamarugite on the map
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