Wheatleyite

Chemical formula: Na₂Cu²⁺((C₂)⁶⁺O₄)₂·2H₂O

Wheatleyite is a rare, organic copper mineral characterized by its distinctive bright blue color and low hardness.

## Characteristics Wheatleyite is a hydrated sodium and copper oxalate, belonging to a rare group of organic minerals. It forms aggregates of small, platy or acicular crystals, which rarely exceed 1 mm in length. Its most characteristic feature is its intense, bright blue color, which distinguishes it from the host rock. ## Physical Properties This mineral is very soft, with a Mohs hardness of only 1-2, meaning it can be scratched with a fingernail. It has a relatively low density, about 2.27 g/cm³. Crystals exhibit a vitreous luster and are usually translucent. ## Colors and Varieties Wheatleyite occurs exclusively in shades of bright blue. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1986 by Arthur E. Smith Jr. and Donald R. Peacor. Its name comes from its discovery locality – the Wheatley Mine (Wheatley Mines) in Chester County, Pennsylvania, USA. This is a historic lead mine, known for the occurrence of many rare secondary minerals. ## Uses Due to its rarity, small crystal size, and low hardness, wheatleyite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities.

Properties

Mohs hardness
1-2
Luster
Vitreous
Streak
Light blue
Density
2.27
Cleavage
{100}; two additionally observed optically.
Fracture
Uneven
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification The key diagnostic features are its bright blue color, very low hardness (1-2 on the Mohs scale), and specific occurrence in the oxidation zones of ore deposits. It reacts with acids and is sparingly soluble in water. ## Distinguishing from similar minerals It can be confused with other blue secondary copper minerals, such as chalcanthite or linarite. However, chalcanthite is readily soluble in water and has a different crystal habit. Linarite is significantly harder (2.5) and has a higher density. Final differentiation often requires advanced analysis. ## Crystal forms Wheatleyite forms prismatic, platy, or acicular crystals, often aggregated into radiating clusters, rosettes, or crusts. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation zones of ore deposits, mainly lead and copper. Its formation results from the reaction of copper-rich solutions with oxalic acid, which can originate from the decomposition of organic matter (e.g., lichens) or from interaction with sedimentary rock minerals. ## Mineral associations At its type locality (Wheatley Mine), it co-occurs with anglesite, cerussite, pyromorphite, sphalerite, and quartz. In other locations, it has been found in association with moolooite. ## Localities The most important and type locality is the historic Wheatley Mines in Pennsylvania, USA. Additionally, its presence has been reported in several other places worldwide, including the Mooloo Downs mine in Western Australia and mines in the Tuscany region of Italy. All these occurrences are very limited. ## Collectors ## Quality criteria The most prized specimens are those with visible, even microscopic, crystals of intense blue color, forming aesthetic aggregates on a contrasting substrate (rock matrix). Due to the small size of the crystals, specimens are usually "micromount" or "thumbnail" type. Purity is not a key criterion; the form and abundance of occurrence on the specimen are what matter. ## Popular localities By far the most sought-after and classic specimens come from the type locality – the Wheatley Mine in Pennsylvania, USA. Specimens from this location have historical and reference value for systematic collectors and specialists in rare minerals.

Rarity

Very rare

For collectors

## Kryteria jakości Najbardziej cenione okazy to te z widocznymi, choćby mikroskopijnymi, kryształami o intensywnie niebieskiej barwie, tworzącymi estetyczne agregaty na kontrastującym podłożu (matrycy skalnej). Ze względu na mały rozmiar kryształów, okazy są zazwyczaj typu "micromount" lub "thumbnail". Czystość nie jest kluczowym kryterium, liczy się forma i bogactwo występowania na okazie. ## Popularne stanowiska Zdecydowanie najbardziej poszukiwane i klasyczne okazy pochodzą z lokalizacji typowej – kopalni Wheatley w Pensylwanii, USA. Okazy z tego miejsca mają wartość historyczną i referencyjną dla kolekcjonerów systematycznych i specjalistów od rzadkich minerałów.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to its water solubility, contact with water, especially hot water, should be avoided. Ultrasonic cleaning is absolutely forbidden. ## What to avoid Avoid contact with water and all chemicals. The mineral is very soft and brittle, so it must be protected from impacts, scratching, and abrasion. It should not be heated or exposed to prolonged strong light. ## Storage Wheatleyite specimens are best stored in closed, padded "micromount" boxes to protect them from mechanical damage, dust, and moisture. It should not be stored loosely with harder minerals.

External references

Sources

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