Mineral
Adamite
Zn₂(AsO₄)(OH)Adamit
Zinc arsenate in fan-shaped crystals from honey yellow to green: some specimens glow under ultraviolet light.
- Popularly: Common stone
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In short
Adamite is a mineral made of zinc, arsenic, oxygen and hydrogen (Zn₂(AsO₄)(OH)). It is pale yellow, honey yellow or green and often crystallises in radiating sprays and fan-shaped groups. It forms in the parts of zinc- and arsenic-bearing deposits exposed to air. Some specimens glow lemon yellow under ultraviolet light. It is named after the French mineralogist Gilbert-Joseph Adam, who supplied the first specimens.
Photos
How does it form?
Adamite is a secondary mineral: it forms in the oxidised zone of zinc- and arsenic-bearing deposits made by hot water solutions (hydrothermal fluids), the part near the surface exposed to air and water. That is why it occurs with smithsonite, hemimorphite, scorodite, olivenite, calcite, quartz and iron–manganese oxides. Copper, cobalt, nickel or manganese can take the place of zinc in its structure; its copper-bearing kinds form a series with olivenite.
According to the Handbook of Mineralogy, large crystals come from the Ojuela mine at Mapimí in Mexico and from Tsumeb in Namibia. Zimapán and Santa Eulalia in Mexico, the Cap Garonne mine in France, the Clara mine in Germany’s Black Forest, the Kamariza mine at Lavrio in Greece and Cornwall in England are among its other known localities.
What is it used for?
- Collecting: Its vivid colours and fan-shaped crystal groups make it sought after by collectors.
- Fluorescence: Because some specimens glow under ultraviolet light, it features in collections of fluorescent minerals.
What determines its value?
Adamite is valued not as an ore but as a collector's mineral. Collectors look for vividly coloured, lustrous, large crystals, fan-shaped groups, specimens that glow strongly under ultraviolet light, and the green copper-bearing or pink cobalt-bearing kinds. The best-known specimens come from the Ojuela mine in Mexico.
This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.
How to recognise it
- 1
Pale yellow, honey yellow, brownish yellow or green; copper-bearing kinds can be bright green and cobalt-bearing kinds pink or purple.
- 2
Its crystals often form radiating sprays, fan-shaped groups or crystalline crusts.
- 3
Vitreous lustre; transparent to translucent.
- 4
Its hardness is 3.5; a knife scratches it.
- 5
Some specimens glow lemon yellow under short- and long-wave ultraviolet light.
Fakes and imitations
What shops usually don’t tell you:
- Olivenite is a green copper arsenate found in the same deposits, and it forms a series with adamite; telling green adamite from olivenite with certainty takes chemical analysis.
Safety
Adamite contains arsenic. According to the World Health Organization, inorganic arsenic causes cancer in humans, and long-term exposure leads to serious health problems. Do not put adamite in your mouth, grind, sand or heat it, breathe its dust or put it in drinking water. Wash your hands after handling it and keep specimens out of reach of children.
Myths and misconceptions
MythEvery yellow-green mineral that glows under ultraviolet light is radioactive.
FactFluorescence and radioactivity are different things. Adamite can glow under ultraviolet light but is not radioactive; some uranium minerals, such as autunite, both glow and are radioactive. Only a radiation meter can tell whether a stone is radioactive.
Did you know?
Adamite was first described in 1866 from Chañarcillo in Chile.
The Ojuela mine in Mexico has yielded 117 mineral species; its adamite, in a wide range of colours and habits, sets the benchmark for collectors.
Its crystals can grow up to 8 cm.
Where is it found?
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- Ojuela mine, Mapimí, Durango, Mexico · Major depositFamous for large crystals; its adamite in many colours and habits sets the benchmark for collectors
- Chañarcillo, near Copiapó, Atacama, Chile · Type localityAdamite was first described in 1866 from specimens found here (coordinate is Copiapó; the mine lies south of the town)
- Tsumeb, Oshikoto, Namibia · Known localityYields large crystals, according to the Handbook of Mineralogy
- Lavrio (Laurium), Attica, Greece · Known localityThe ancient silver-mining district; adamite occurs in the Kamariza mine here
Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →
Frequently asked questions
What is adamite?
Adamite is a mineral made of zinc, arsenic, oxygen and hydrogen (Zn₂(AsO₄)(OH)). It is pale yellow, honey yellow or green and often crystallises in radiating sprays and fan-shaped groups. It forms in the parts of zinc- and arsenic-bearing deposits exposed to air. Some specimens glow lemon yellow under ultraviolet light. It is named after the French mineralogist Gilbert-Joseph Adam, who supplied the first specimens.
Why is adamite sometimes green and sometimes pink?
Other metals can partly take the place of zinc in adamite's structure. Copper gives a bright green colour, cobalt a pink or purple one. Pure adamite is pale yellow or colourless.
What is adamite used for?
Collecting: Its vivid colours and fan-shaped crystal groups make it sought after by collectors. Fluorescence: Because some specimens glow under ultraviolet light, it features in collections of fluorescent minerals.
How hard is adamite?
It has a hardness of 3.5 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 4.32–4.48 g/cm³.
Where is adamite found?
Its best-known localities: Chañarcillo, near Copiapó, Atacama, Chile; Ojuela mine, Mapimí, Durango, Mexico; Tsumeb, Oshikoto, Namibia; Lavrio (Laurium), Attica, Greece.
How can you tell if adamite is real?
Pale yellow, honey yellow, brownish yellow or green; copper-bearing kinds can be bright green and cobalt-bearing kinds pink or purple. Its crystals often form radiating sprays, fan-shaped groups or crystalline crusts. Vitreous lustre; transparent to translucent. Olivenite is a green copper arsenate found in the same deposits, and it forms a series with adamite; telling green adamite from olivenite with certainty takes chemical analysis.
Is adamite valuable?
On the “street to diamond” value ladder it sits on step 3 of nine: Building and industrial stone. Adamite is valued not as an ore but as a collector's mineral. Collectors look for vividly coloured, lustrous, large crystals, fan-shaped groups, specimens that glow strongly under ultraviolet light, and the green copper-bearing or pink cobalt-bearing kinds. The best-known specimens come from the Ojuela mine in Mexico.
Is adamite dangerous?
Adamite contains arsenic. According to the World Health Organization, inorganic arsenic causes cancer in humans, and long-term exposure leads to serious health problems. Do not put adamite in your mouth, grind, sand or heat it, breathe its dust or put it in drinking water. Wash your hands after handling it and keep specimens out of reach of children.
Sources
- Adamite · Wikipedia
- Handbook of Mineralogy: Adamite · Mineralogical Society of America
- Ojuela · Wikipedia
- Arsenic (fact sheet) · World Health Organization
External links
ReviewedLast checked: 4 October 2026
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