Xocomecatlite

Chemical formula: Cu²⁺₃Te⁶⁺O₄(OH)₄

Xocomecatlite is a rare copper tellurate, forming characteristic spherical aggregates of an intensely emerald-green color.

## Characteristics Xocomecatlite is a secondary copper tellurate found in the oxidation zones of ore deposits. Its most characteristic visual feature is the clusters of tiny, acicular or bladed crystals that form spherical or hemispherical aggregates with a radial internal structure. Individual crystals are usually microscopic in size, and their clusters rarely exceed a few millimeters in diameter. This mineral is prized for its intense, emerald-green color. ## Physical Properties Xocomecatlite crystals are very small and brittle. The mineral is characterized by a vitreous luster. Due to the microscopic size of the crystals and the porosity of the aggregates, precise determination of hardness and density is difficult; the calculated density is 4.59 g/cm³. ## Colors and Varieties This mineral occurs exclusively in one color – intense, emerald-green. No color or commercial varieties are distinguished. ## History and Name The name xocomecatlite comes from the Nahuatl word *xocomecatl*, meaning "grape vines," which alludes to the appearance of its spherical, green aggregates. The mineral was first described in 1975 by S.A. Williams based on samples from the Oriental mine in Moctezuma, Sonora, Mexico. ## Uses Xocomecatlite has no industrial application. It is solely a mineral of scientific and collecting interest.

Properties

Mohs hardness: 4
Color: emerald-green
Luster: Vitreous
Streak: Light green to white
Density: 4.65
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification The diagnostic feature of xocomecatlite is its unique, spherical aggregates with a radial structure, composed of tiny, acicular crystals of a vivid, emerald-green color. Occurrence in association with other copper tellurates and tellurides is also a key indicator. ## Distinguishing from Similar Minerals Xocomecatlite is sometimes confused with other green secondary copper minerals such as brochantite, malachite, or agardite. However, its form of occurrence distinguishes it – perfectly spherical aggregates with a radial internal structure are very characteristic. Malachite forms fibrous or botryoidal clusters, but rarely perfectly spherical ones. Final confirmation requires chemical analysis (presence of tellurium). ## Crystal Forms The mineral forms very fine, elongated crystals with an acicular or bladed habit. These crystals almost always occur as radial clusters, forming spherical or hemispherical aggregates that grow on the host rock.

Geological environment

## Genesis Xocomecatlite is a secondary mineral, forming in the oxidation zones of hydrothermal deposits rich in tellurium and copper. It forms as a result of the weathering of primary tellurides, most often in vugs and fissures of volcanic rocks, such as rhyolite. ## Mineral Associations This mineral often co-occurs with other rare tellurates and tellurides. Typical associated minerals include mckinstryite, emmonsite, spiroffite, tennantite, as well as quartz, barite, and native gold. ## Localities The most important and classic locality, from which the best specimens originate, is the Oriental mine in Moctezuma (Sonora, Mexico). This mineral has also been identified in several locations in the USA, including mines in Cochise and La Paz counties in Arizona, and in the El Plomo mine in Honduras.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized xocomecatlite specimens are characterized by numerous, well-formed, perfectly spherical aggregates of an intense, emerald-green color. Contrast with a light host rock (matrix) and the absence of damage to the delicate spheres are important. The size of the aggregates is also significant – specimens with spheres exceeding 1-2 mm in diameter are considered exceptional. ## Popular Localities By far the most sought-after specimens by collectors come from the type locality – the Oriental mine in Moctezuma, Mexico. This locality has yielded the best quality and largest aggregates of this mineral.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Any contact with water or chemicals is highly inadvisable. Due to extreme delicacy, touching the acicular crystals should be avoided. ## What to Avoid Absolutely avoid contact with water, acids, detergents, and other cleaning agents. Aggregates are very brittle and sensitive to shocks and abrasion. Specimens should not be exposed to ultrasound. ## Storage It is recommended to store specimens in closed, stable containers (such as "micromount boxes") to protect them from dust, mechanical damage, and sudden changes in humidity. Display should be away from areas prone to vibrations.