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Tarapacáite is a rare potassium chromate mineral primarily found in the hyper-arid regions of Chile. It typically forms small, yellow, tabular crystals or crusts within nitrate-rich evaporite deposits and is highly soluble in water.

Hardness
2
Mohs
Luster
Vitreous
Streak
Light yellow
Transparency
Transparent

Is this tarapacáite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

  • 1
    Test the hardness
    Try to scratch tarapacáite with a known reference. Tarapacáite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
  • 2
    Check the streak
    Drag the specimen across an unglazed porcelain plate. Streak: light yellow.
  • 3
    Read the luster
    Hold the specimen under a strong light. Luster: vitreous.
  • 4
    Match the color range
    Compare against the expected color range: yellow, light yellow.
  • 5
    Look at form & habit
    Crystal system: orthorhombic. Typical habit: tabular crystals, massive, crusts.

Often confused with

Tarapacáite vs. its common look-alikes, and how to tell them apart in the field.

Crocoite mineral
mineral
Crocoite
Mohs 2.5-3

How to tell apart: Streak differs, so Tarapacáite leaves light yellow, Crocoite leaves yellow-orange; luster reads vitreous on Tarapacáite and adamantine on Crocoite.

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Often found alongside tarapacáite

Minerals reported to co-occur with tarapacáite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula
K₂CrO₄
Mohs hardness
2
Density
2.74 g/cm³
Colors
YellowLight yellow
Streak
Light yellow
Luster
Vitreous
Transparency
Transparent
Crystal system
Orthorhombic
Crystal habit
Tabular crystals, massive, crusts
Cleavage
On {010} and {100}, distinct
Rarity
Rare
Uses
Collector
Host rock
A minor accessory mineral in nitrate deposits

Where rockhounds find tarapacáite

Classic worldwide localities

  • Nitrate caliche deposits throughout the Atacama Desert, as at the Oficina Maria Elena, near Tocopilla, Antofagasta, and Zapiga, Tarapacá, Chile

Field-hunting tip

Where it forms: A minor accessory mineral in nitrate deposits. If you start seeing lopezite, dietzeite in float, you are in the right ground. Typical habit: tabular crystals, massive, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tarapacáite?+
Mohs hardness is 2. Luster: vitreous. The streak is light yellow. Common colors include yellow, light yellow.
Where is tarapacáite found?+
Notable localities include Nitrate caliche deposits throughout the Atacama Desert, as at the Oficina Maria Elena, near Tocopilla, Antofagasta, and Zapiga, Tarapacá, Chile.
Is tarapacáite safe to handle?+
Tarapacáite contains hexavalent chromium and calls for real care. Contains chromium in the hexavalent state, which is toxic and a known carcinogen. Wash hands thoroughly after handling and avoid inhaling dust.
What rocks look like tarapacáite?+
Tarapacáite is most often confused with Crocoite. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with tarapacáite?+
Tarapacáite commonly co-occurs with Lopezite, Dietzeite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does tarapacáite form in?+
Where it forms: A minor accessory mineral in nitrate deposits. Working float back to the host body is the standard way to chase a fresh occurrence.
What is tarapacáite used for?+
Tarapacáite is used in collector.

Find tarapacáite on the map

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