Juabite
Chemical formula: CaCu²⁺₁₀(Te⁴⁺O₃)₄(As⁵⁺O₄)₄(OH)₂·4H₂O
Juabite is a very rare, emerald-green copper-calcium tellurite-arsenate, forming small, tabular crystals.
Properties
- Mohs hardness
- 3-4
- Luster
- Vitreous , Adamantine
- Streak
- Pale green
- Density
- 0
- Cleavage
- {010}
- Fracture
- Irregular/Uneven,Sub-Conchoidal
- Transparency
- Transparent,Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Juabite can be identified by its characteristic emerald-green color, small, tabular crystals forming rosette-like aggregates, and its association with other rare minerals from the oxidized zone of tellurium ores. A light green streak is also a helpful feature. ## Distinguishing from Similar Minerals It can be confused with other green, secondary copper minerals, such as brochantite, malachite, or other rare arsenates and tellurites. Definitive differentiation requires advanced analytical methods (e.g., EDS/XRD) due to visual similarities and co-occurrence. It is distinguished from malachite by its lack of reaction with hydrochloric acid. ## Crystal Forms Crystals are usually very small, tabular or bladed in habit, often flattened. They typically occur as radial or rosette-like clusters and aggregates on the matrix rock.
Geological environment
## Genesis Juabite is a secondary mineral, forming in the oxidation (weathering) zone of polymetallic ore deposits rich in tellurium, arsenic, and copper. It forms in voids and fissures in rocks, most often quartz. ## Mineral Associations This mineral co-occurs with other rare minerals of the oxidized zone. At the type locality, it was found in association with quartz, barite, enargite, tennantite, as well as rarer tellurites and arsenates such as dugganite, xocomecatlite, mcalpineite, and eztlite. ## Localities Juabite is an extremely rare mineral, known from only a few localities worldwide. The most important and type locality is the Centennial Eureka mine in Eureka, Juab County, Utah, USA. Its occurrence has also been confirmed in the Aga mine in Yamaguchi Prefecture, Japan.
Rarity
Very rare
For collectors
## Quality Criteria The most prized juabite specimens are those with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. The intensity and saturation of the emerald-green color significantly increase its value. Contrast with a light matrix rock (most often quartz) and the presence of rare associated minerals are also important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. ## Popular Localities The only source of collectible specimens is the historic type locality – the Centennial Eureka mine in Utah, USA. Specimens from this mine are highly sought after by collectors specializing in rare minerals and "micromounts."
Care and storage
## Cleaning Juabite specimens are extremely delicate and small. Cleaning should be kept to an absolute minimum. If necessary, compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and any chemical agents. ## What to Avoid Ultrasonic cleaners, chemicals, acids, and even water should be strictly avoided, as they can damage delicate crystals or the matrix rock. The mineral is soft and brittle, susceptible to scratches and mechanical damage. It should be protected from high temperatures and direct sunlight. ## Storage Juabite specimens should be stored under stable conditions, preferably in a sealed "micromount" box, which protects against dust, shocks, and sudden changes in humidity. Display should be away from sources of vibration and direct light.