Spertiniite
Chemical formula: Cu<sup>2+</sup>(OH)<sub>2</sub>
Spertiniite is a copper(II) hydroxide, forming characteristic blue, spherulitic aggregates and coatings.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- Pale blue
- Density
- 3.1
- Cleavage
- Perfect on {100}, good on {010} and {001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Spertiniite is most easily recognized by its characteristic form – blue, spherical or hemispherical aggregates (spherulites) with a radial internal structure. Its intense blue color and occurrence as a secondary mineral in association with other copper minerals are key indicators. ## Distinguishing from Similar Minerals It can be confused with other blue, secondary copper minerals. It differs from **chrysocolla** by its more defined, spherulitic structure (chrysocolla is usually amorphous, gel-like). It differs from **azurite** in form (azurite more often forms distinct tabular crystals or granular aggregates) and a slightly lighter, more "milky" shade of blue. Reaction with acids can be helpful, but this is a destructive method. ## Crystal Forms Spertiniite forms microscopic, elongated crystals with an acicular or platy habit. These crystals almost always occur in the form of radial or fibrous aggregates, which arrange into characteristic spherulites (spheres) or hemispheres, and also form coatings and crusts.
Geological environment
## Genesis Spertiniite is a secondary mineral, forming in the oxidation (weathering) zones of copper ore deposits. It forms as a result of the reaction of copper-rich solutions with surrounding rocks under low temperature and pressure conditions. It is a product of the weathering of chalcopyrite and other copper sulfides. ## Mineral Associations It most commonly co-occurs with other minerals of the oxidation zone, such as chalcopyrite (as a primary mineral), malachite, azurite, brochantite, atacamite, as well as with rock-forming minerals, e.g., diopside, vesuvianite, and grossular, especially in skarn environments. ## Localities The most important and classic locality, from which the best specimens originate, is the Jeffrey Mine in Val-des-Sources (formerly Asbestos) in Quebec, Canada. Other known localities include the Kombat Mine in Namibia; Laurion in Greece; and several places in Germany (e.g., in the Harz Mountains).
Rarity
Rare
For collectors
## Quality Criteria The most desirable spertiniite specimens are characterized by well-formed, complete spherulites of intense, uniform blue color. Specimens showing numerous, undamaged spheres contrasting with the color of the host rock are highly valued. The aesthetic composition and lack of mechanical damage to the delicate aggregates are also important. ## Popular Localities Specimens from the type locality – the Jeffrey Mine in Quebec, Canada – are by far the most valued and sought after by collectors. They are considered the global standard for this mineral.
Care and storage
## Cleaning Spertiniite specimens are very delicate. They should only be cleaned using compressed air to remove dust. Any contact with water or liquids is inadvisable, as it can damage the fragile aggregates. ## What to Avoid Avoid contact with water, acids, and any chemicals that may react with copper hydroxide. The mineral is susceptible to mechanical damage, so avoid vibrations, impacts, and friction. Do not clean it with ultrasound. ## Storage It is recommended to store specimens in closed, padded "micromount" boxes to protect them from dust and mechanical damage. Avoid exposure to moisture and direct sunlight.