Utahite

Chemical formula: MgCu²⁺₄Zn²⁺₂Te⁶⁺₃O₁₄(OH)₄·₆H₂O

Utahite is a very rare copper, magnesium, and zinc tellurate, forming microscopic, platy crystals of an intense blue color.

## Characteristics Utahite is a hydrated copper, magnesium, and zinc tellurate. It occurs as very small, thin, platy crystals with a hexagonal outline, rarely exceeding 0.2 mm. It forms rosette-like aggregates, thin crusts, or appears as single, scattered crystals on the host rock. Due to its size, a microscope is essential for its observation. ## Physical Properties Utahite crystals are flexible and can be bent. The Mohs hardness is low, approximately 2-3. The luster is vitreous, and the crystals are transparent. The density calculated based on the chemical formula and unit cell parameters is 4.25 g/cm³. ## Colors and Varieties This mineral is characterized by a uniform, intense, azure or indigo-like blue color. It has no known varieties. ## History and Name Utahite was discovered in the Centennial Eureka gold mine in the Tintic District, Juab County, Utah, USA. It was described and approved as a new mineral by the International Mineralogical Association (IMA) in 1997. Its name comes directly from the state of Utah, where its type locality is situated.

Properties

Mohs hardness: 4-5
Color: Light blue, blue-green
Luster: Vitreous , Adamantine
Streak: Pale blue
Density: 0
Cleavage: Perfect on {0001}
Fracture: Irregular/Uneven
Transparency: Transparent,Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Utahite is primarily identifiable by its unique chemical composition, which requires advanced analysis (e.g., EDS). Visually, it is characterized by an intense blue color, platy crystal habit, and occurrence in the form of small, rosette-like aggregates. Its co-occurrence with other rare tellurates is also characteristic. ## Distinguishing from Similar Minerals It can be confused with other blue secondary minerals, such as azurite, linarite, or cyanotrichite. It differs from azurite by its lack of reaction with hydrochloric acid. Distinguishing it visually from linarite and cyanotrichite is practically impossible without chemical analysis, although utahite forms characteristic hexagonal, platy crystals, while cyanotrichite occurs in acicular aggregates. ## Crystal Forms The crystals are thin, platy, with a hexagonal outline. They usually form rosette-like or radial aggregates, as well as thin coatings and crusts on the rock surface.

Geological environment

## Genesis Utahite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits, especially those rich in tellurium. It forms as a result of the alteration of primary tellurides in the presence of solutions rich in copper, zinc, and magnesium. ## Mineral Associations It most commonly co-occurs with other rare tellurates and sulfates, such as xocomecatlite, jensenite, leisingite, cesbronite, as well as with quartz, barite, pyrite, and enargite. ## Localities This is an extremely rare mineral. Besides its type locality in the Centennial Eureka mine in Utah (USA), its occurrence has been confirmed in only a few other places worldwide, including the Bambolla mine (Bambollita) in Moctezuma, Sonora state, Mexico.

Rarity

Very rare

For collectors

## Quality Criteria The quality of utahite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates. Most prized are specimens with clearly formed, undamaged rosettes of intense blue color, contrasting with a light host rock. Due to the microscopic size of the crystals, their abundance on a given matrix fragment is crucial. ## Popular Localities The best and most well-known specimens come from the type locality – the Centennial Eureka mine in Utah, USA. Specimens from the Mexican Bambolla mine are also sought after by collectors specializing in rare minerals and "micromounts."

Care and storage

## Cleaning Utahite specimens are extremely delicate and susceptible to mechanical damage. Cleaning is not recommended. Any attempts to remove dust should be limited to very careful use of a soft brush or a photographic air blower, without touching the crystals. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. The crystals are very soft and brittle, so they must be protected from any pressure, vibrations, or scratching. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, which protect them from dust, shocks, and mechanical damage. Store in a dry place, away from direct sunlight and heat sources.