Lotharmeyerite
Chemical formula: CaZn<sup>2+</sup><sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O
Lotharmeyerite is a rare zinc and calcium arsenate, forming small, orange-red crystals, prized by collectors of rare minerals.
Properties
- Mohs hardness
- 3
- Luster
- Vitreous
- Streak
- Pale yellow
- Density
- 4.1-4.19
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Lotharmeyerite can be identified by its characteristic orange-red color, small, tabular crystals forming radial aggregates, and its occurrence in the oxidation zones of polymetallic deposits. Its relatively low hardness (approximately 3) is also a helpful feature. ## Distinguishing from Similar Minerals It can be confused with other arsenates from the tsumcorite group, such as gartrellite or tsumcorite, which often co-occur and have similar forms. Definitive differentiation requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). Visually, it may also resemble some microcrystalline varieties of wulfenite or vanadinite, but it differs from them in crystal habit and environment of occurrence. ## Crystal Forms Crystals are usually very small, with a tabular or bladed habit, often flattened. They form characteristic radial or stellate aggregates, as well as thin crusts and coatings on rock surfaces.
Geological environment
## Genesis Lotharmeyerite is a secondary mineral, formed in the oxidation zones (gossans) of polymetallic ore deposits rich in arsenic and zinc. It forms as a result of the weathering of primary ore minerals, such as sphalerite and arsenopyrite. ## Mineral Associations This mineral often co-occurs with other rare arsenates, such as adamite, köttigite, legrandite, scorodite, smithsonite, tsumcorite, and gartrellite. In its type locality (Ojuela Mine), it was found in association with legrandite and adamite. ## Localities The most important and well-known lotharmeyerite localities worldwide include: - Mexico: Ojuela Mine, Mapimí, Durango (type locality). - Chile: Veta Negra Mine, Copiapó, Atacama. - Germany: Clara Mine in Wolfach, Black Forest. - Greece: Mines in the Laurion region, Attica.
Rarity
Rare
For collectors
## Quality Criteria Specimens with well-formed, sharp crystals forming aesthetic, radial aggregates are most valued by collectors. An intense, orange-red color is a key factor increasing value. Contrast with the rock matrix and the presence of rare associated minerals are also important. Due to the small size of the crystals, specimens are usually intended for "micromount" collections. ## Popular Localities The most famous and desirable lotharmeyerite specimens come from the type locality – the Ojuela Mine in Mexico. Specimens from the Clara Mine in Germany and Laurion in Greece are also prized by specialists.
Care and storage
## Cleaning Specimens should be cleaned only with extreme care, using a soft brush to remove dust. Due to its brittleness and solubility in acids, contact with water and any chemical agents should be avoided. The safest method is dry cleaning. ## What to Avoid Absolutely avoid contact with water, acids, and other chemicals that can damage or dissolve the mineral. Lotharmeyerite is brittle, so it must be protected from impacts and vibrations. It should also not be heated. ## Storage Lotharmeyerite specimens are best stored in sealed, stable containers (e.g., "micromount" type) that protect them from dust, moisture, and mechanical damage. Avoid exposure to direct sunlight, although there is no evidence of fading.