Whelanite

Chemical formula: Cu²⁺₂Ca₆[Si₆O₁₇(OH)](CO₃)(OH)₃·2H₂O

Whelanite is a very rare, hydrated copper calcium silicate, distinguished by its pale blue color and perfect cleavage.

## Characteristics Whelanite is a complex, hydrated copper calcium silicate, belonging to the very rare minerals. It forms small, bladed or fibrous crystals, which often aggregate into rosettes or spherulites. Its characteristic feature is a delicate, pale blue or greenish-blue color, giving it a subtle appearance. Due to its rarity and small crystal size, it is a mineral known mainly in scientific circles and among specialized collectors. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2.5, making it susceptible to scratching. It has a density of 2.74 g/cm³, typical for hydrated silicates. Whelanite is transparent, and its luster is described as vitreous. It exhibits perfect cleavage in one direction and good cleavage in another, which, combined with its splintery fracture, contributes to its fragility. ## Colors and Varieties The dominant color of whelanite is pale blue, sometimes transitioning into greenish-blue hues. This variation depends on subtle fluctuations in chemical composition. No named varieties of this mineral have been identified. ## History and Name The mineral's name honors James A. Whelan (1924-1985), a professor of geology at the University of Utah in the USA, in recognition of his contributions to the study of the geology and mineral resources of that state. Whelanite was described and approved as a new mineral species in 1978. ## Uses Due to its extreme rarity and occurrence as small crystals, whelanite has no industrial application. Its significance is purely scientific and for collectors.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
Pale blue
Density
2.74
Cleavage
perfect on {001} and good on {010}
Fracture
Splintery
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Key diagnostic features of whelanite include its pale blue color, fibrous or bladed crystal habit forming rosette aggregates, low hardness (2.5), and occurrence in a specific geological environment. A pale blue streak is also helpful in identification. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of similar color, such as aurichalcite or rosasite. Whelanite differs from them in crystal form (blades, not needles as in aurichalcite), lower hardness, and unique chemical composition, which requires advanced analyses (e.g., XRD, EDS) for definitive confirmation. ## Crystal Forms Whelanite forms elongated, bladed crystals that aggregate into radial, rosette, or spherulitic (spherical aggregates) forms. It rarely occurs as single, well-formed crystals.

Geological environment

## Genesis Whelanite is a secondary mineral, forming in the oxidation zones of polymetallic deposits. It forms as a result of hydrothermal solutions acting on carbonate rocks in the presence of copper compounds. In its type locality, it formed in calcite veins cutting through volcanic rhyolite tuffs. ## Mineral Associations This mineral co-occurs with other secondary minerals. In its type locality, it was found in association with calcite, quartz, stringhamite, junitoite, and blue chalcedony. ## Localities The only confirmed and described occurrence of whelanite in the world is its type locality – the Bawana Mine in Beaver County, Utah, USA. This is a "type locality" site, which makes it extremely important from a scientific point of view.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a whelanite specimen is primarily judged by the intensity and purity of its pale blue color and the aesthetics of its aggregates. The most desirable specimens are those with distinct, well-formed rosettes or spherulites on a contrasting matrix, most often on calcite. The size of crystals and aggregates is also important, although even small specimens are highly valued. ## Popular Localities The only source of whelanite specimens is the Bawana Mine in Utah, USA. All samples available on the collector's market come from this single location, which drives up their value and makes them extremely difficult to acquire.

Care and storage

## Cleaning Whelanite specimens should be cleaned with utmost care, using only compressed air to remove dust. Due to its softness and reactivity, the use of water, even distilled, and any mechanical tools, such as brushes, is discouraged. ## What to Avoid The mineral is very sensitive. Contact with all chemicals, including acids and detergents, should be avoided. It is unstable at elevated temperatures, which can lead to its dehydration and destruction of its structure. It should also be protected from moisture and direct sunlight. ## Storage It is recommended to store whelanite in stable conditions, in a closed, padded "micromount" box, to protect it from mechanical damage, dust, and changes in humidity. It is not suitable for display in open showcases.

External references

Sources

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