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

Mohs

Luster

Vitreous

Streak

Yellow

Transparency

Transparent

mineralrare

Tarapacáite

Hardness: 2
Luster: Vitreous
Streak: Yellow
Transparency: Transparent

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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. Tarapacáite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Tarapacáite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, orange-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.

mineral

Crocoite

Mohs 2.5-3

How to tell apart: Streak differs — Tarapacáite leaves yellow, Crocoite leaves orange-yellow; 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: 2.71 g/cm³
Colors: Yellow Orange-yellow
Streak: Yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Massive, Crusts
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Arid Evaporite Deposits
Typical price: $50-300 per specimen

Where rockhounds find tarapacáite

Classic worldwide localities

Tarapacá, Chile
Atacama Desert, Chile

Field-hunting tip

Look in arid evaporite deposits country — that is the host setting where tarapacáite typically forms. If you start seeing dietzeite, nitratine, gypsum in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tarapacáite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is yellow. Common colors include yellow, orange-yellow.

Where is tarapacáite found?+

Notable localities include Tarapacá, Chile; Atacama Desert, Chile.

How much is tarapacáite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is tarapacáite safe to handle?+

It contains toxic constituents. Contains chromium in the hexavalent state, which is toxic and a known carcinogen. Wash hands thoroughly after handling and avoid inhaling dust. Handle with care, avoid grinding or breathing dust, and store separately.

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 Dietzeite, Nitratine, Gypsum, Halite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tarapacáite form in?+

Tarapacáite typically forms in arid evaporite 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

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.