Erythrite is a secondary mineral often called 'cobalt bloom' because it forms as bright pink to crimson crusts on weathered cobalt-arsenide deposits. It is best known for its delicate, acicular prismatic crystals or radiating sprays, though these are extremely fragile and must be handled with great care.

Hardness

1.5-2.5

Mohs

Luster

Adamantine to Pearly

Streak

Pale Pink

Transparency

Translucent

mineraluncommonVivianite Group family

Erythrite

Also: Cobalt Bloom, Red Cobalt

Hardness: 1.5-2.5
Luster: Adamantine to Pearly
Streak: Pale Pink
Transparency: Translucent

Is this erythrite?

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 erythrite with a known reference. Erythrite sits at Mohs 1.5-2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Erythrite leaves a pale pink streak.
3
Read the luster
Hold the specimen under a strong light. Erythrite typically shows a adamantine to pearly luster.
4
Match the color range
Compare against the expected color range: crimson, peach-red, pink, violet.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular crystals, radiating sprays, crusts, earthy coatings.

Often confused with

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

mineral

Vivianite

Mohs 1.5-2

How to tell apart: Streak differs, so Erythrite leaves pale pink, Vivianite leaves white to light blue; luster reads adamantine to pearly on Erythrite and vitreous on Vivianite.

Compare →

Often found alongside erythrite

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

All properties

Chemical formula: Co₃(AsO₄)₂·8H₂O
Mohs hardness: 1.5-2.5
Density: 3.0-3.1 g/cm³
Colors: Crimson Peach-red Pink Violet
Streak: Pale Pink
Luster: Adamantine to Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Acicular Crystals, Radiating Sprays, Crusts, Earthy Coatings
Cleavage: Perfect On {010}
Rarity: Uncommon
Uses: Collector, Indicator Mineral
Host rock: Oxidized Zones of Arsenic-cobalt Ore Deposits
Typical price: $20-200 depending on crystal size and location

Where rockhounds find erythrite

1 mapped spots

Classic worldwide localities

Bou Azzer (Morocco)
Schneeberg (Germany)
Cobalt (Canada)
Laurion (Greece)

Field-hunting tip

Look in oxidized zones of arsenic-cobalt ore deposits country, the host setting where erythrite typically forms. If you start seeing cobaltite, skutterudite, arsenopyrite in float, you are in the right ground. Field specimens usually show a acicular crystals, radiating sprays, crusts, earthy coatings habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.

Browse 1 U.S. spots for erythrite →

Common questions

How do you identify erythrite?+

Mohs hardness is 1.5-2.5. It typically shows a adamantine to pearly luster. The streak is pale pink. Common colors include crimson, peach-red, pink, violet.

Where is erythrite found?+

Notable localities include Bou Azzer (Morocco); Schneeberg (Germany); Cobalt (Canada); Laurion (Greece).

Can I find erythrite in the United States?+

RockHoundR maps 1 erythrite rockhounding spots across 1 U.S. states. The top states are Wyoming.

How much is erythrite worth?+

Typical asking prices fall in the range of $20-200 depending on crystal size and location. Quality, size, and provenance can move individual specimens well outside that range.

Is erythrite safe to handle?+

It contains toxic constituents. Contains arsenic and cobalt; wash hands thoroughly after handling and avoid inhaling dust or powder. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like erythrite?+

Erythrite is most often confused with Vivianite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with erythrite?+

Erythrite commonly co-occurs with Cobaltite, Skutterudite, Arsenopyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does erythrite form in?+

Erythrite typically forms in oxidized zones of arsenic-cobalt ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is erythrite used for?+

Erythrite is used in collector, indicator mineral.

Find erythrite on the map

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