Rodalquilarite

Chemical formula: H₃Fe₃+₂(Te₄+O₃)₄Cl

Rodalquilarite is a rare iron tellurite with a characteristic emerald-green color, found in the oxidation zones of gold-bearing hydrothermal deposits.

## Characteristics Rodalquilarite is a secondary mineral from the tellurite group, valued for its intense, emerald-green or yellowish-green color. It typically forms small, tabular or short-prismatic crystals with a hexagonal outline, rarely exceeding a few millimeters. Most often, it occurs as fine-grained aggregates, crusts, and coatings on the host rock. Its crystals exhibit a strong, almost adamantine luster, which, combined with its vivid color, makes it an attractive micromount mineral. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 2.5-3, meaning it is susceptible to scratching. It exhibits perfect cleavage in one plane, parallel to the crystal base. The fracture is conchoidal. The density of rodalquilarite is significant, approximately 4.0 g/cm³. The luster is described as adamantine to resinous, and the mineral can be transparent or translucent. ## Colors and Varieties Characteristic of rodalquilarite is a range of colors from emerald green to yellowish-green hues. The intensity and shade depend on impurities and specific crystallization conditions. No named commercial or color varieties are distinguished. ## History and Name The mineral's name comes from its discovery location – the gold mine in Rodalquilar, Almería province, Spain. It was first described in 1968 by a team of mineralogists: J. Sierra López, G. Pericay, J. La Iglesia, and F.J. Bosch. ## Uses Rodalquilarite has no industrial applications. Its significance is purely scientific and collectible, and specimens are sought after due to their rarity, beautiful color, and interesting paragenesis, especially with native gold.

Properties

Mohs hardness: 2.5-3
Luster: Adamantine to resinous
Streak: Light green
Density: 4.0
Cleavage: Perfect on {0001}
Fracture: Conchoidal
Transparency: Transparent to translucent
Crystal system: Trigonal

Diagnostic features

## Identification The most important diagnostic features of rodalquilarite are its unique emerald-green color, strong adamantine luster, and specific occurrence environment – the oxidation zones of tellurium deposits. Hardness (low) and perfect cleavage are also helpful in identification. ## Distinguishing from Similar Minerals Rodalquilarite can be confused with other green secondary minerals: - **Emmonsite**: Another iron tellurite, often accompanying rodalquilarite. However, it usually has a more yellowish-green or olive hue and a different crystal structure. - **Malachite**: Has similar hardness but is a carbonate and reacts vigorously with hydrochloric acid, unlike rodalquilarite. It also usually has a different, more "grassy" shade of green and often forms botryoidal or radial aggregates. - **Annabergite**: Is a nickel arsenate and occurs in a completely different geological environment (oxidation zones of nickel deposits). Its luster is usually more pearly or dull. ## Crystal Forms Rodalquilarite crystallizes in the trigonal system, forming small, hexagonal in outline, tabular or short-prismatic crystals. It is most commonly found as druses and crusts composed of densely packed, tiny crystals.

Geological environment

## Genesis Rodalquilarite is a secondary mineral, forming in the oxidation zones of hydrothermal gold and tellurium deposits. It forms as a result of weathering and alteration of primary tellurium-bearing minerals (e.g., native tellurium, sylvanite, krennerite) in the presence of iron- and chloride-rich solutions. ## Mineral Associations This mineral often occurs in association with other rare minerals of the oxidation zone. Its typical associations include: native gold, native tellurium, emmonsite, mackayite, alunite, jarosite, barite, and quartz. ## Localities The most important and classic locality is the gold mine in Rodalquilar, Spain, from which the best specimens originate. Significant finds also come from the El Indio deposit in Chile. The mineral has also been reported in Japan (Kawazu mine), Mexico (Moctezuma), and the United States (e.g., Cochise County in Arizona and the Cripple Creek district in Colorado).

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized rodalquilarite specimens are characterized by an intense, emerald-green color and well-formed, lustrous crystals. Contrast with the matrix is of great importance – green crystals on white quartz or barite are particularly sought after. The presence of visible native gold in the paragenesis drastically increases the value and attractiveness of the specimen. Due to the small size of the crystals, it is primarily a mineral for collectors specializing in micromounts. ## Popular Localities Specimens from the type locality – Rodalquilar, Spain – are considered the best in the world. They are historically the most important and serve as the standard for this mineral. Very good quality crystals, often in association with gold, also come from the El Indio deposit in Chile.

Care and storage

## Cleaning Rodalquilarite specimens are very delicate and should be handled with care. To remove dust, it is best to use a soft brush or compressed air from a safe distance. Avoid washing in water, and if absolutely necessary, use only distilled water and dry the specimen immediately. Ultrasonic cleaners should never be used. ## What to Avoid The mineral is soft and has perfect cleavage, making it very sensitive to impacts, drops, and scratches. Avoid contact with all chemicals, especially acids. As a chloride, it may be sensitive to prolonged exposure to moisture. It should not be exposed to high temperatures or sudden thermal changes. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to protect them from mechanical damage and dust. Exposure should be in stable conditions, away from direct sunlight, heat sources, and in a low-humidity environment.