Attikaite

Chemical formula: Ca<sub>3</sub>Cu<sup>2+</sup><sub>2</sub>Al<sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>4</sub>(OH)<sub>4</sub>·2H<sub>2</sub>O

Attikaite is a very rare, hydrated calcium, copper, and aluminum arsenate, forming characteristic, sky-blue, spherical aggregates.

## Characteristics Attikaite is a mineral from the arsenate group, characterized by an intense, blue color. It occurs as small, spherical or hemispherical aggregates with a radial internal structure. The individual crystals forming these aggregates are extremely small, acicular or bladed, which gives the surface of the aggregates a delicate, silky luster. Due to its rarity and attractive appearance, it is a prized collector's mineral. ## Physical Properties Attikaite crystals are too small to examine their properties individually. Aggregates are relatively soft, with a hardness of about 2-2.5 on the Mohs scale. The luster of the aggregates is silky to dull. The mineral is opaque. ## Colors and Varieties Attikaite occurs in a characteristic, light blue or sky-blue color. No color or commercial varieties have been distinguished. ## History and Name The mineral's name comes from the Attica region in Greece, where its type locality is located – the ancient mines of Lauríon (Lavrion). It was approved as a new mineral by the International Mineralogical Association (IMA) in 2006 (IMA2006-039). It was described by a team of mineralogists: N. V. Chukanov, I. V. Pekov, D. A. Varlamov, D. I. Belakovskiy, P. Y. M. Rowe, R. S. W. Braithwaite, and A. K. Krivovichev. ## Uses Attikaite has no industrial application. Its only significance is scientific and as a collector's item.

Properties

Mohs hardness
2-2.5
Luster
Silky
Streak
Light blue
Density
3.16
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of attikaite include its unique occurrence in the form of sky-blue, spherical aggregates with a radial internal structure and a silky luster. Its occurrence in the oxidation zones of polymetallic deposits, especially in association with other arsenates, is a strong diagnostic indicator. ## Distinguishing from Similar Minerals Attikaite is sometimes confused with other blue secondary minerals. It is distinguished from chalcanthite by its insolubility in water. It is distinguished from aurichalcite by its lack of reaction with hydrochloric acid. From the blue variety of smithsonite (hemimorphite), it is usually softer and has a different aggregate structure (radial spheres instead of crusts or botryoidal aggregates). Final confirmation requires advanced analytical methods (XRD, EDS). ## Crystal Forms This mineral forms spherical or hemispherical aggregates, reaching up to several millimeters in diameter. They are composed of very fine, acicular or bladed crystals arranged radially from a common center.

Geological environment

## Genesis Attikaite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits rich in arsenic. It forms as a result of the reaction of solutions containing arsenate ions with copper, aluminum, and calcium minerals, under conditions of low temperature and pressure. It most often occurs in voids and fissures in rocks. ## Mineral Associations This mineral co-occurs with other rare secondary minerals, such as olivenite, conichalcite, azurite, malachite, gypsum, aragonite, goethite, and also with other arsenates, e.g., from the mixite group. ## Localities The most important and type locality for attikaite is the historical mines in the Lauríon (Lavrion) district in the Attica region, Greece. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The most prized attikaite specimens are those with well-formed, spherical aggregates of intense blue color, contrasting with the rock matrix. The size and number of spherical aggregates on the specimen, as well as the absence of mechanical damage, are important. Specimens with a well-defined radial internal structure are particularly sought after. ## Popular Localities The only source of collector's specimens of attikaite is the mines in the Lauríon region of Greece. Material from this locality is extremely rare and highly valued in the collector's market.

Care and storage

## Cleaning Attikaite specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to its softness and potential reactivity, contact with water, and especially chemicals, should be avoided. If liquid is necessary, the surface can be very gently wiped with a cotton swab minimally moistened with isopropyl alcohol, taking care that the liquid does not penetrate the aggregate structure. ## What to Avoid Ultrasonic cleaners, all acids, and detergents, which can chemically damage the mineral, must be absolutely avoided. Attikaite is soft and brittle, making it very susceptible to mechanical damage, scratches, and chipping. It should be protected from high temperatures and direct sunlight, which can cause dehydration and color change. ## Storage Attikaite specimens are best stored in separate, padded display boxes to avoid contact with harder minerals. They should be kept in stable conditions, away from moisture, dust, and heat sources.

External references

Sources

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