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 — 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 — that is 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.