Grandviewite

Chemical formula: Cu<sup>2+</sup><sub>3</sub>Al<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)(OH)<sub>10</sub>·H<sub>2</sub>O

Grandviewite is a very rare, secondary copper and aluminum mineral with a characteristic pale blue color, occurring as microscopic crystals.

## Characteristics Grandviewite is a hydrated copper and aluminum hydroxyl sulfate. It occurs as very small, bladed or tabular crystals, rarely exceeding 0.2 mm in length. These crystals form rosette-like aggregates, spherical clusters, or thin coatings and crusts on the host rock. Due to the microscopic size of the crystals, its visual features are difficult to assess without magnification. ## Physical Properties Grandviewite crystals are flexible and exhibit perfect unidirectional cleavage. The mineral has a hardness of approximately 2.5-3 on the Mohs scale and a pale blue streak. The luster is vitreous to pearly on cleavage surfaces. It is a light mineral, with a calculated density of 3.15 g/cm³. ## Colors and Varieties Grandviewite has a characteristic pale blue to blue-green color. No varieties have been distinguished. ## History and Name The mineral was first described in 1998 by William W. Pinch, Robert A. Gault, and Joel D. Grice. Its name comes from its discovery location – the Grand View Mine in Coconino County, Arizona, USA, which is also its type locality. This mine is located within the Grand Canyon National Park. ## Uses Grandviewite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
2.5-3
Luster
Vitreous to Pearly
Streak
Pale blue
Density
3.15
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Field identification of Grandviewite is impossible due to the microscopic size of its crystals. In a collection, it is recognized by its characteristic pale blue, rosette-like aggregates on the host rock, originating from its only known location. Certain identification requires advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. ## Distinguishing from Similar Minerals It can be confused with other secondary blue copper minerals, such as cyanotrichite, chalcoalumite, or ktenasite. Differentiation is mainly possible based on chemical and crystallographic analysis. Grandviewite is distinguished by its unique composition and crystal structure. ## Crystal Forms It forms very small, elongated, bladed crystals, often flattened. These crystals combine into characteristic, radial or rosette-like aggregates and spherulitic (spherical) clusters.

Geological environment

## Genesis Grandviewite is a secondary mineral, formed in the oxidation (weathering) zone of copper deposits. It forms in a dry, desert climate as a result of sulfate-rich solutions acting on copper and aluminum minerals. At its type locality, it formed on the walls of old mine workings. ## Mineral Associations This mineral co-occurs with other secondary sulfates and copper minerals. At the Grand View Mine, it has been found in association with cyanotrichite, chalcoalumite, brochantite, malachite, azurite, ktenasite, gypsum, and minerals from the allophane group. ## Localities The only confirmed occurrence of Grandviewite in the world is the Grand View Mine, located in the Grand Canyon, Arizona, USA. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of Grandviewite specimens is primarily assessed based on the richness and aesthetics of the microscopic aggregates on the rock matrix. The most prized specimens are those with clearly formed, undamaged rosettes or spherical clusters of an intense, pale blue color. Contrast with the substrate and the presence of associated minerals are also important. ## Popular Localities The only source of Grandviewite specimens is its type locality - the Grand View Mine in Arizona, USA. All specimens available on the collector's market come from this single location.

Care and storage

## Cleaning Grandviewite specimens are extremely delicate and consist of microscopic crystals. They should not be cleaned mechanically or chemically. Any attempts at cleaning, even with water, can destroy the delicate aggregates. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and any vibrations or impacts. The mineral is sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight. ## Storage Specimens should be stored only in sealed, padded "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Display is possible only under stable conditions, away from sources of vibration.

Sources

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