Erythrite
The Cobalt Bloom
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Quick Facts
Formation & Origin
Erythrite is a hydrated cobalt arsenate mineral (Co₃(AsO₄)₂·8H₂O), known for the crimson-pink crusts and blooms that signal cobalt ore. Erythrite forms as a secondary mineral in the oxidation zone of cobalt-arsenic ore deposits. When cobalt arsenide minerals like skutterudite and cobaltite are exposed to weathering, the released cobalt and arsenic combine with water to form erythrite's vivid pink-purple crystals.
The characteristic color is so distinctive that prospectors and miners have long used erythrite as a guide to hidden cobalt ore deposits. This prospecting use earned it the name 'cobalt bloom.' The presence of vivid pink crusts or crystal sprays on rock surfaces signals that cobalt-arsenic ores lie beneath.
Morocco's Bou Azzer district produces the world's finest erythrite crystals, which can form prismatic crystals several centimeters long with intense crimson color and vitreous luster. These are highly sought by mineral collectors.
Identification Guide
Erythrite is identified by its vivid crimson-pink to purple-pink color, very low hardness (1.5-2.5), and association with cobalt-arsenic mining environments. Crystal habit is prismatic to acicular, often in radiating sprays or earthy crusts.
Distinguish from cobaltocalcite (effervesces in acid, different crystal system), rhodochrosite (harder, different streak), and roselite (similar color, different crystal habit). The combination of vivid pink color and extreme softness in a mining context is diagnostic. SAFETY: Contains arsenic. Handle carefully.
Spotting Fakes
Erythrite is not commonly faked. The main concern is quality and integrity. Moroccan specimens are the most prized, with large, well-formed crystals on matrix commanding premium prices. Earthy, crusty erythrite is much less valuable than crystallized material. Some specimens may be washed or cleaned with chemicals that can damage delicate crystal faces. Ask about cleaning history for high-value specimens.
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Cultural & Metaphysical Traditions
Presented as cultural traditions, not scientific evidence
Erythrite is considered a stone of love, vitality, and harmonious relationships in crystal healing. Its vivid pink color connects it to heart-centered energy. Practitioners use it for enhancing emotional intelligence and nurturing partnerships. IMPORTANT: Contains both cobalt and arsenic. Display specimen only. Handle with care and wash hands after. Do not make gem elixirs.
Metaphysical and “healing” associations are cultural traditions, not medical advice or scientific fact. Crystals are not a substitute for professional medical care.
Where It's Found
World's finest crystals, vivid crimson color
Excellent specimens from cobalt mines
Historic silver-cobalt mining district
Classic European locality
Price Guide
Good to Know
Scratch test: At hardness 2, Erythrite can be scratched with a fingernail. This is a display specimen, not a wearable stone.
Global supply: Found in 4 notable locations worldwide, from Morocco to Germany.
Heft test: Erythrite has average mineral density (3.06). It feels about as heavy as you'd expect from a stone its size.
Common Questions
What is the chemical formula of Erythrite?
The chemical formula of Erythrite is Co₃(AsO₄)₂·8H₂O.
What is Erythrite's Mohs hardness?
Erythrite has a Mohs hardness of 2 on the 1 to 10 Mohs scale, soft enough to scratch with a fingernail.
Is Erythrite a mineral?
Yes. Erythrite is a naturally occurring mineral (Arsenate Mineral) with a definite chemical composition and an ordered crystal structure.
Care & Safety
The water, salt, and sunlight questions people actually ask before cleansing or displaying erythrite, answered from its hardness (Mohs 2) and chemistry (Co₃(AsO₄)₂·8H₂O).
Can Erythrite go in water?
Not recommended. At Mohs 2, erythrite is soft enough that water can slowly dull, etch, or wear down the surface, so a water cleanse does more harm than good here. Reach for a dry cloth instead. Important: erythrite contains cobalt and arsenic. Never use it for gem elixirs or crystal-infused water, and wash your hands after handling it.
Can Erythrite go in salt water?
No. Erythrite is best kept away from water altogether, and salt water is the harsher version of that problem: the dissolved salt is corrosive while the stone is wet, then leaves gritty crystals behind in cracks and crevices as it dries.
Sources & References
The mineralogical and gemological data on this page is drawn from and can be cross-checked against these external references.
- WikipediaErythrite on Wikipedia
- WebmineralErythrite mineral data (Webmineral)
- Handbook of MineralogyErythrite (Handbook of Mineralogy, PDF)
Related Minerals
Another pink cobalt mineral, calcite-based
Nickel arsenate, green equivalent of erythrite
Primary cobalt ore that weathers to erythrite
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