Adamite

See 1 specimen in the collection

Identity

Formula Zn₂(AsO₄)(OH)

Class Arsenates

Crystal System Orthorhombic

Hardness 3.5

Color Yellow, honey, green, also pink and purple

Lustre Vitreous

Specific Gravity 4.4

Cleavage Good on {101}

Streak White to pale green

Technical notes (click to open)(click to close)

Cause of color Iron gives yellow to honey shades, copper gives green, and cobalt or manganese give pink to purple

Fluorescence Many specimens glow strong green to yellow green under ultraviolet light, a collector highlight

Occurrence A secondary mineral of the oxidized zone in zinc deposits that also carry arsenic, often on brown limonite with smithsonite and hemimorphite

Series Forms a series with the copper arsenate olivenite; the intermediate member is the separate species zincolivenite

Crystal habit Stubby prisms, bladed crystals, and radiating or globular clusters, often as crusts on matrix

Toxicity A zinc arsenate; wash hands after handling and never grind or breathe the dust

Name & Human History

Etymology

Adamite is a zinc mineral with a glow that makes it a favorite among collectors. The French chemist Charles Friedel named it in 1866. He did not name it for himself. He named it for Gilbert-Joseph Adam, a wealthy French collector who supplied the very first specimens. The mineral honors the man who brought it to science, a quiet custom that has named many minerals.

Today

Adamite is mostly a collector's mineral today. It forms bright crystals in shades of yellow, honey, and green. They often crowd together in little fans and crusts on rusty brown rock. Many specimens glow a brilliant green under ultraviolet light, which has made adamite a star of fluorescent displays. Like other minerals that contain arsenic, it is handled with care and kept away from food and children.

Geology & Occurrence

Formation

Adamite forms late and near the surface, as a so called secondary mineral. It appears where older zinc ores slowly break down in air and water, and where arsenic is also present. The dissolved zinc and arsenic recombine in cracks and cavities to grow fresh adamite crystals. These often line the walls of a pocket. Its color shifts with the trace metals it carries. Iron tints it yellow, copper turns it green, and cobalt can push it toward pink or purple.

Notable Localities

The most famous adamite in the world comes from the Ojuela mine near Mapimi, in Durango, Mexico. There it grows in glowing yellow and green clusters. The mineral was first described from Chile, its original home. Fine pieces also come from the old mines at Lavrion in Greece, and from Tsumeb in Namibia, one of the great mineral localities on Earth.

Did you know?

Adamite is one of the standout stones of any fluorescent collection. In ordinary daylight a specimen may look like a soft yellow crust, pretty but quiet. Switch on an ultraviolet lamp in a dark room and the same piece blazes a vivid lime green. It can be bright enough to light up the table. Collectors who specialize in glowing minerals often build a whole display around a single fine adamite.

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Adamite