Coralloite is a rare manganese arsenate mineral that forms distinctive, coral-like botryoidal aggregates. It is primarily found in specialized hydrothermal environments rich in manganese and arsenic, often associated with secondary manganese minerals.

Hardness

3-4

Mohs

Luster

Vitreous

Transparency

Translucent

mineralrare

Coralloite

Hardness: 3-4
Luster: Vitreous
Transparency: Translucent

No image

Is this coralloite?

4-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 coralloite with a known reference. Coralloite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: cinnabar-red.
4
Look at form & habit
Crystal system: triclinic. Typical habit: botryoidal, crusts, radial aggregates.

Often confused with

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

How to tell apart: Luster reads vitreous on Coralloite and adamantine to greasy on Pharmacosiderite.

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Often found alongside coralloite

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

All properties

Chemical formula: MnMn₂(AsO₄)₂(OH)₂·4H₂O
Mohs hardness: 3-4
Density: 3.26 g/cm³
Colors: Cinnabar-red
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Botryoidal, crusts, radial aggregates
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral in strataform manganese deposits

Where rockhounds find coralloite

Classic worldwide localities

Monte Nero Mine, Rocchetta Vara, La Spezia, Liguria, Italy, Switzerland
Falotta and Alpe Tanatz, Switzerland

Field-hunting tip

Where it forms: A secondary mineral in strataform manganese deposits. If you start seeing calcite, inesite, quartz in float, you are in the right ground. Typical habit: botryoidal, crusts, radial aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify coralloite?+

Mohs hardness is 3-4. Luster: vitreous. Common colors include cinnabar-red.

Where is coralloite found?+

Notable localities include Monte Nero Mine, Rocchetta Vara, La Spezia, Liguria, Italy, Switzerland; Falotta and Alpe Tanatz, Switzerland.

Is coralloite safe to handle?+

Coralloite contains arsenic and calls for real care. Contains arsenic, a toxic element. Wash hands thoroughly after handling and avoid creating dust or inhaling particles.

What rocks look like coralloite?+

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

What minerals are found with coralloite?+

Coralloite commonly co-occurs with Calcite, Inesite, Quartz, Brandtite, Sarkinite, Tilasite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does coralloite form in?+

Where it forms: A secondary mineral in strataform manganese deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is coralloite used for?+

Coralloite is used in collector.

Find coralloite on the map

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