Pinalite

Chemical formula: Pb<sup>2+</sup><sub>3</sub>(W<sup>6+</sup>O<sub>4</sub>)OCl<sub>2</sub>

Pinalite is a rare secondary mineral from the tungstate group, characterized by orange-red, prismatic crystals and occurrence in the oxidation zones of lead deposits.

## Characteristics Pinalite is a rare, secondary lead and tungsten mineral. It forms characteristic, small, prismatic crystals up to 1 mm long, which often occur as radial or tangled aggregates. Its most recognizable feature is its intense, orange-red color. ## Physical Properties Pinalite crystals exhibit a luster ranging from vitreous to greasy. The mineral is transparent to translucent. Due to the small size of the crystals, hardness and density have not been precisely determined, but the density is estimated to be high, which is typical for lead minerals. ## Colors and Varieties Pinalite occurs in a characteristic range of colors from orange, through orange-red, to red. No varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality – the Old Yuma Mine in Pinal County, Arizona, USA. It was described and approved as a new mineral species in 1989 by a team of mineralogists comprising: Donald R. Peacor, Pete J. Dunn, William B. Simmons Jr., and Robert A. Ramik. ## Uses Due to its extreme rarity and small crystal size, pinalite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals and micromounts.

Properties

Luster
Vitreous to Greasy
Streak
Orange
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Pinalite is identified primarily by its unique combination of features: intense orange-red color, prismatic crystal habit, high luster, and co-occurrence with other secondary lead minerals in a specific geological environment. ## Distinguishing from similar minerals Pinalite can be confused with wulfenite, especially its microcrystalline varieties. However, it is distinguished by its prismatic crystal habit (wulfenite forms tabular crystals) and specific mineral associations. It differs from mimetite and vanadinite in crystal habit and chemical composition. ## Crystal Forms It forms elongated, prismatic crystals, often terminated by a pyramid. The crystals are usually very small and occur as radial or chaotically arranged aggregates on the surface of the host rock.

Geological environment

## Genesis Pinalite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal polymetallic deposits rich in lead. Its crystallization occurs as a result of reactions between tungsten-bearing solutions and primary lead minerals in the presence of chloride ions. ## Mineral Associations This mineral often co-occurs with other secondary lead minerals, such as cerussite, anglesite, wulfenite, mimetite, as well as with quartz, hematite, and limonite. ## Localities The most important and type locality for pinalite is the Old Yuma Mine in the Saguaro District, Pinal County, Arizona, USA. This is the only locality from which well-formed, collectible specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The most prized pinalite specimens are characterized by rich clusters of well-formed, intensely colored, orange-red crystals, contrasting with a light matrix rock (most often quartz). The size of the crystals, their luster, and lack of damage significantly increase their collectible value. ## Popular Localities The only source of valuable collectible pinalite specimens is its type locality – the Old Yuma Mine in Arizona, USA. Specimens from this location are considered classic for this species.

Care and storage

## Cleaning Pinalite specimens should be cleaned very carefully, using only compressed air to remove dust. Contact with water and any chemical agents should be avoided. ## What to avoid The mineral is sensitive to chemicals, especially acids. Ultrasonic cleaning, steam cleaning, and sudden temperature changes should be avoided. The crystals are very fragile and susceptible to mechanical damage. ## Storage It is recommended to store specimens in stable conditions, in enclosed "micromount" boxes, to protect them from dust, physical damage, and moisture. Exposure to direct sunlight should be avoided.

External references

Sources

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