Reichenbachite
Chemical formula: Cu<sup>2+</sup><sub>5</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>4</sub>
Reichenbachite is a rare copper hydroxyphosphate, forming microscopic, dark green crystals and coatings, prized by collectors of rare minerals.
Properties
- Mohs hardness
- 3
- Luster
- Vitreous
- Streak
- Light green
- Density
- 4.35
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Reichenbachite is identified by its characteristic dark green color, its occurrence in the form of small, tabular crystals forming rosette-like aggregates, and its association with other secondary copper minerals. Its high density is also a helpful characteristic. However, definitive identification requires advanced research methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Reichenbachite is a polymorph of pseudomalachite and ludjibite, meaning it has an identical chemical composition. Distinguishing it from these minerals is impossible without specialized crystallographic studies. Visually, it can be confused with other secondary copper minerals, such as malachite, brochantite, or libethenite. It differs from malachite by its lack of reaction with hydrochloric acid (it does not effervesce), and from the others by subtle differences in hue and crystal form. ## Crystal Forms Reichenbachite crystals are very small, usually tabular or bladed, flattened parallel to the {001} plane. They often form fan-shaped, radial, or rosette-like clusters and aggregates.
Geological environment
## Genesis Reichenbachite is a secondary copper mineral that forms in the oxidation (weathering) zones of copper ore deposits. It forms as a result of the action of phosphate-rich waters on primary copper minerals, such as chalcopyrite or bornite. It is a mineral of the supergene zone. ## Mineral Associations This mineral often co-occurs with other secondary copper minerals and phosphates. The most common associated minerals include: pseudomalachite, libethenite, malachite, cornetite, quartz, barite, and goethite. ## Localities The most important and type locality for reichenbachite is the Reichenbach mine in Odenwald (Hesse, Germany), from which the best specimens originate. It is also known from several other localities worldwide, including the Miguel Vacas mine in Portugal, the Spring Creek mine in South Australia, and several places in the Democratic Republic of Congo (e.g., the L'Etoile du Congo mine).
Rarity
Rare
For collectors
## Quality Criteria The collector's appeal of reichenbachite specimens primarily depends on the quality and size of the crystals, although these rarely reach significant dimensions. Most valued are specimens with well-formed, sharp crystals forming aesthetic, rosette-like aggregates of an intense green color. Contrast with the rock matrix and the presence of rare associated minerals are also important. Undamaged specimens with a distinct luster are rated higher. ## Popular Localities Undoubtedly, the most classic and prized locality for this mineral is the Reichenbach mine in Germany. Specimens from there are considered benchmark examples for this species and fetch the highest prices in the collector's market.
Care and storage
## Cleaning Reichenbachite specimens should be cleaned with the utmost care, using only compressed air to remove dust. Due to its brittleness and small crystal size, contact with water and brushes, which could mechanically damage the delicate aggregates, should be avoided. ## What to Avoid This mineral is sensitive to acids, which can chemically damage it. Ultrasonic cleaners, sudden temperature changes, and prolonged exposure to moisture should be avoided. ## Storage It is recommended to store specimens in closed, stable containers ("membrane box" type boxes or cotton wool) to protect them from dust, shocks, and mechanical damage. Display should be in conditions of stable humidity and away from direct sunlight.