Science Fair Project Encyclopedia
Adamite
This article is about the mineral, for the religious sect see Adamites.
| Adamite | |
|---|---|
|
Yellow-green adamite in limonite. | |
| General | |
| Category | Mineral |
| Chemical formula | Zn2AsO4OH |
| Identification | |
| Color | Yellow, green, rarely white, and occasionally purple |
| Crystal habit | Wedge-like prisms typically in druses and radiating clusters - also smooth botryoidal masses. |
| Crystal system | Orthorhombic; 2/m 2/m 2/m |
| Cleavage | perfect in two directions |
| Fracture | conchoidal. |
| Mohs Scale hardness | 3.5 |
| Luster | adamantine |
| Refractive index | nα=1.708 - 1.722 nβ=1.742 - 1.744 nγ=1.763 - 1.773 |
| Pleochroism | . |
| Streak | white to pale green |
| Specific gravity | 4.4 |
| Other Characteristics | Strongly fluoresces green in short and long UV light. |
Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Adamite is usually yellow in color, but tints of green occur due to inclusion of copper substitutions in the mineral structure. Olivinite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.
The yellow to bright lime-green colored crystals and druze along with its distinctive fluorescence make adamite a favorite among mineral collectors. Found in Mapimi, Mexico; Greece; and California and Utah in the United States.
Adamite was named after the French mineralogist Gilbert Joseph Adam (1795-1881). The type locality is in the Atacama Desert in Chile.
References
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