Nickellotharmeyerite
Chemical formula: CaNi²⁺₂(As⁵⁺O₄)₂·2H₂O
Nickel-lotharmeyerite is a rare hydrated calcium nickel arsenate from the tsumcorite group, forming small, transparent brown or yellow crystals.
Properties
- Mohs hardness
- 4.5
- Luster
- Subadamantine
- Streak
- light brown to yellow
- Density
- 0
- Fracture
- Conchoidal
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Field identification of nickel-lotharmeyerite is practically impossible due to its microscopic size. In a collection, it is recognized by its characteristic, small, tabular crystals of brown or yellow color and subadamantine luster, gathered in radial aggregates. Association with the locality is key – it occurs in oxidation zones of nickel and cobalt ores. ## Distinguishing from Similar Minerals It can be confused with other arsenates from the tsumcorite group, such as cobalt-lotharmeyerite (usually pink or purple), zinc-lotharmeyerite (colorless, white), or lotharmeyerite (orange, reddish-brown). Definitive differentiation from these minerals requires advanced chemical analysis (EDS) to confirm the dominance of nickel. ## Crystal Forms Crystals are very small, typically tabular or bladed, often flattened. They form characteristic radial or stellate aggregates, as well as thin crusts and rosettes on rock surfaces.
Geological environment
## Genesis Nickel-lotharmeyerite is a secondary mineral, forming in oxidation (weathering) zones of ore deposits rich in arsenic, nickel, and cobalt. It forms as a result of reactions between solutions containing these elements and calcium-rich rocks. ## Mineral Associations This mineral coexists with other rare arsenates, such as erythrite, annabergite, pharmacosiderite, arseniosiderite, gersdorffite, skutterudite, nickelskutterudite, quartz, and iron and manganese oxides. ## Localities The most important and type locality is the historical mines in the Schneeberg area in Saxony (Germany), especially the Pucher shaft. Beyond this locality, its presence has been confirmed in several other places worldwide, including the Bou Azzer mines in Morocco and the Cobalt-Gowganda area in Ontario (Canada).
Rarity
Very rare
For collectors
## Quality Criteria The most prized specimens are those with well-formed, sharp crystals forming aesthetic, radial aggregates or rosettes. A contrasting, undamaged host rock significantly increases the specimen's value. Due to the microscopic nature of the mineral, the quality of the "micromount" – meaning the aesthetics of the entire specimen under magnification – is crucial. Color intensity and luster also contribute to its attractiveness. ## Popular Localities Specimens from the type locality – the Pucher shaft in Schneeberg, Germany – are by far the most sought after by collectors. They are considered classic and serve as a benchmark for this mineral.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Any contact with water or a brush is risky due to the microscopic size and fragility of the crystals. If liquid is necessary, isopropyl alcohol applied precisely, e.g., with a pipette, is recommended, avoiding soaking the host rock. ## What to Avoid Avoid contact with water, acids, and other chemicals. The mineral is sensitive to shocks and abrasions, which can damage delicate crystals. It should not be heated or exposed to prolonged strong light. ## Storage Nickel-lotharmeyerite specimens should be stored in stable conditions, in enclosed "micromount" boxes that protect them from dust, humidity, and mechanical damage. Display should be away from sources of vibration and direct sunlight.