Erythrite is a striking mineral, primarily identified as a hydrated cobalt arsenate, well-known for its vivid pink coloration. Miners have historically recognized it as 'cobalt bloom' due to its frequent association with cobalt ore deposits.
Chemical Composition and Classification
Erythrite is classified within the arsenate mineral group, specifically as a hydrated cobalt arsenate. Its chemical formula is Co₃(AsO₄)₂·8H₂O, indicating its composition of cobalt, arsenic, oxygen, and water molecules. The presence of cobalt within its structure is directly responsible for its distinctive and eye-catching color.
Key Characteristics and Appearance
This mineral is remarkably conspicuous and easily observed, even when present in minuscule quantities, largely owing to its vivid pink to peach-red or crimson hue. This striking color made it a recognizable sign to miners of underlying cobalt. While a number of other similar-coloured cobalt minerals exist, erythrite is generally the most abundant of them.
Here are some of the defining characteristics of erythrite:
- Color: Typically ranges from vivid pink to peach-red or crimson.
- Historical Name: Widely known by miners as 'cobalt bloom', reflecting its often efflorescent, crusty appearance in weathered cobalt-bearing veins.
- Luster: Displays a pearly to vitreous (glassy) luster, particularly on cleavage surfaces.
- Hardness: Relatively soft, with a Mohs hardness of 1.5 to 2.5, meaning it can be easily scratched with a fingernail or copper coin.
- Crystal System: Forms in the monoclinic system, often appearing as prismatic to acicular (needle-like) crystals, though it is more commonly found as earthy crusts, radiating aggregates, or powdery coatings.
Geological Occurrence and Significance
Erythrite is a secondary mineral, meaning it forms from the alteration of other primary cobalt-bearing minerals. It is typically found in the oxidized zones of cobalt-rich ore deposits. Its presence often serves as an important indicator of underlying cobalt mineralization, making it valuable for mineral exploration. It can be found in association with other cobalt, nickel, and arsenic minerals.
| Property | Description |
|---|---|
| Mineral Name | Erythrite |
| Classification | Hydrated Cobalt Arsenate |
| Chemical Formula | Co₃(AsO₄)₂·8H₂O |
| Color | Vivid Pink, Peach-Red, Crimson |
| Hardness (Mohs) | 1.5 - 2.5 |
| Luster | Pearly to Vitreous |
| Crystal System | Monoclinic |
| Historical Name | 'Cobalt Bloom' |
| Significance | Indicator mineral for cobalt ore deposits |
Erythrite's distinct color and clear association with cobalt have made it a notable mineral for both mineralogists and prospectors, providing a visual cue for the presence of valuable cobalt resources.
