Creaseyite

Chemical formula: Pb₂(Cu,Fe)₂Zn(Si₂O₇)(OH)₂

Creaseyite is a rare secondary silicate mineral, forming characteristic, acicular aggregates of a blue-green color.

## Characteristics Creaseyite is a hydrated lead, copper, zinc, and iron silicate. It most often occurs as small, acicular or fibrous crystals that form radial aggregates, rosettes, or felt-like crusts. Its color is usually vibrant, ranging from green to blue-green, which makes it a visually attractive micromount mineral. ## Physical Properties Creaseyite crystals are typically too small to accurately examine their properties without specialized equipment. This mineral is relatively soft, with a hardness of about 4 on the Mohs scale. It has a vitreous luster, sometimes slightly greasy on fresh surfaces. It is a translucent mineral and quite heavy due to its lead content. ## Colors and Varieties Creaseyite occurs in shades from green to blue-green. The intensity and hue of the color depend on the ratio of copper to iron in its structure. No named commercial or color varieties are distinguished. ## History and Name The mineral was first described in 1975 by Sidney A. Williams and Richard A. Bideaux. Its name honors S. C. Creasey (1915-1987), a geologist with the United States Geological Survey (USGS), for his contributions to the study of Arizona geology. The type locality is the Mammoth-St. Anthony mine in Tiger, Arizona, USA. ## Uses Due to its rarity and occurrence in small quantities, creaseyite has no industrial application. It is of scientific and collector's interest only, being a prized acquisition in collections of rare minerals and micromounts.

Properties

Mohs hardness
4
Luster
Vitreous to greasy
Streak
Light green
Density
4.45
Cleavage
None
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Creaseyite is identified by its characteristic appearance – radial aggregates of small, acicular crystals of a blue-green color. The identification of associated minerals, typical of the oxidation zones of ore deposits, is also crucial. ## Distinguishing from Similar Minerals Creaseyite is sometimes confused with other secondary copper minerals: - **Chrysocolla**: Usually amorphous and has a lower luster. Creaseyite forms distinct, though small, crystals. - **Shattuckite**: Has a very similar color and also forms fibrous aggregates. Reliable differentiation of these two minerals often requires advanced analyses, e.g., XRD. - **Dioptase**: Forms well-developed, larger rhombohedral crystals and is slightly harder. ## Crystal Forms Creaseyite crystals are acicular or capillary. They almost always occur as radial aggregates, spherical clusters, or tangled felt-like masses. Less commonly, it forms massive or earthy aggregates.

Geological environment

## Genesis Creaseyite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of polymetallic hydrothermal deposits rich in lead, copper, and zinc. It forms as a result of the weathering of primary ore minerals in the presence of silica-rich solutions. ## Mineral Associations This mineral often co-occurs with other secondary minerals of the oxidation zone, such as wulfenite, dioptase, willemite, shattuckite, cerussite, anglesite, chrysocolla, as well as quartz and fluorite. ## Localities The most important and well-known localities of creaseyite in the world include: - **USA**: Mammoth-St. Anthony mine in Tiger, Pinal County, Arizona (type locality). - **Australia**: Bali Lo deposit, Ashburton Shire, Western Australia. - **Italy**: Funtana Raminosa mine, Gadoni, Sardinia.

Rarity

Very rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, radial aggregates of acicular crystals of intense, blue-green color. Highly rated are samples where creaseyite contrasts with the color of the matrix rock or co-occurs with other rare minerals, such as wulfenite or dioptase. ## Popular Localities Specimens from the type locality – the Mammoth-St. Anthony mine in Arizona – are by far the most sought after. This mine has long been closed and flooded, making historical samples very rare and commanding high prices on the collector's market.

Care and storage

## Cleaning Creaseyite specimens are delicate and fragile. They should be cleaned only mechanically, using a soft brush to remove dust. Compressed air can be used from a safe distance. Due to possible reactivity, the use of water, and especially chemical cleaning agents, is not recommended. ## What to Avoid Creaseyite is a soft mineral (hardness 4), so it should be protected from scratching by harder minerals (e.g., quartz). As a lead-containing silicate, it is potentially toxic – hands should be washed after contact with the specimen. Ultrasonic cleaners should be avoided, as they could damage delicate crystal aggregates. ## Storage The best way to store specimens is to place them in a sealed "micromount" box or in a display cabinet, which protects them from dust and mechanical damage. They should be stored separately from harder minerals.

Sources

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