Lammerite
Chemical formula: Cu<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>
Lamerite is a rare copper arsenate, forming characteristic, dark green to black, tabular crystals with a vitreous luster.
Properties
- Mohs hardness
- 3.5-4
- Luster
- Vitreous
- Streak
- Green
- Density
- 4.47-4.51
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of lamerite include its dark green to black color, tabular crystal habit, vitreous luster, and occurrence in the oxidation zones of copper deposits. A green streak is also an important diagnostic clue. ## Distinguishing from Similar Minerals Lamerite is sometimes confused with other secondary copper minerals, such as olivenite, cornwallite, or euchroite. It is distinguished from olivenite by its crystal habit (olivenite forms acicular or prismatic crystals) and a slightly different color. Cornwallite is usually greener and occurs in botryoidal or reniform forms. Euchroite has a lighter, emerald-green color and a different crystal habit. ## Crystal Forms Lamerite crystallizes in the monoclinic system, forming flattened, tabular crystals, often with a hexagonal or octagonal outline. It also occurs as short prisms. Crystals can form fan-shaped or radial aggregates, and also grow on other minerals.
Geological environment
## Genesis Lamerite is a secondary mineral formed in the oxidation (weathering) zones of arsenian copper ore deposits. It forms as a result of reactions of surface waters with primary copper sulfides and arsenides. ## Mineral Associations This mineral often co-occurs with other secondary copper arsenates and sulfates. Its typical associated minerals include euchroite, olivenite, cornwallite, strashimirite, tyrolite, chalcophyllite, as well as tenorite, malachite, and azurite. ## Localities The most important and classic occurrence (type locality) of lamerite is the Reichenbach mine in Odenwald (Hesse, Germany). It is also known from the Clara mine in the Black Forest (Germany) and from small occurrences in Tsumeb, Namibia, and Laurion, Greece.
Rarity
Rare
For collectors
## Quality Criteria Specimens with well-formed, sharp, lustrous crystals of intense, dark green color are most valued by collectors. Rich crystal groups are highly prized, as are aesthetic lamerite growths on contrasting rock matrix or in association with other rare minerals, e.g., euchroite. The size of individual crystals rarely exceeds a few millimeters, so specimens with larger crystals are exceptionally sought after. ## Popular Localities By far the most desirable and classic lamerite specimens come from its type locality - the Reichenbach mine in Germany. Material from this location is considered exemplary for the species.
Care and storage
## Cleaning Lamerite specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided. ## What to Avoid As an arsenate, lamerite is sensitive to acids and other chemicals. Prolonged exposure to moisture, direct sunlight, and high temperatures, which can lead to its degradation, should be avoided. Due to its arsenic content, inhaling dust should be avoided, and hands should be washed after contact with the mineral. ## Storage It is recommended to store specimens in a dry place, in closed boxes or display cases, to protect them from dust and mechanical damage. The mineral's brittleness requires careful handling.