Chinchorroite is a rare secondary arsenate mineral that forms as thin, delicate platy crystals or coatings in oxidized zones of ore deposits. It is primarily found in the Cap Garonne mine of France and requires microscopic examination for positive identification due to its scarcity and small crystal size.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Chinchorroite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this chinchorroite?

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 chinchorroite with a known reference. Chinchorroite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: triclinic. Typical habit: platy crystals, crusts.

Often confused with

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

mineral

Köttigite

Mohs 2-3

How to tell apart: Luster reads vitreous on Chinchorroite and silky on cleavages on Köttigite.

How to tell apart: Legrandite is the harder of the two (Mohs 4.5 vs. 2.5).

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Often found alongside chinchorroite

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

All properties

Chemical formula: Na₂Mg₅(As₂O₇)₂(AsO₃OH)₂(H₂O)₁₀
Mohs hardness: 2.5
Density: 2.75 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Platy crystals, crusts
Cleavage: Very good on {100} and {010}
Rarity: Rare
Uses: Collector
Host rock: hydrothermal polymetallic deposits

Where rockhounds find chinchorroite

Classic worldwide localities

Torrecillas mine, northern Atacama Desert, Salar Grande, Iquique Province, Tarapacá Region, Chile

Field-hunting tip

Where it forms: hydrothermal polymetallic deposits. If you start seeing anhydrite, gypsum, halite in float, you are in the right ground. Typical habit: platy crystals, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify chinchorroite?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include colorless.

Where is chinchorroite found?+

Notable localities include Torrecillas mine, northern Atacama Desert, Salar Grande, Iquique Province, Tarapacá Region, Chile.

Is chinchorroite safe to handle?+

Chinchorroite contains arsenic and calls for real care. Contains arsenic, which is toxic. Wash hands thoroughly after handling and avoid ingestion or inhalation of dust.

What rocks look like chinchorroite?+

Chinchorroite is most often confused with Köttigite, Legrandite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with chinchorroite?+

Chinchorroite commonly co-occurs with Anhydrite, Gypsum, Halite, Talmessite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does chinchorroite form in?+

Where it forms: hydrothermal polymetallic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chinchorroite used for?+

Chinchorroite is used in collector.

Find chinchorroite on the map

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