Lindgrenite

Chemical formula: Cu²⁺₃(Mo⁶⁺O₄)₂(OH)₂

Lindgrenite is a rare, secondary copper and molybdenum mineral, forming characteristic platy crystals of an intense green color.

## Characteristics Lindgrenite is a hydrated copper molybdate, occurring in the oxidation zones of copper-molybdenum deposits. It forms thin, platy or bladed crystals, often aggregated into rosette-like, fan-shaped, or radiating clusters. Sometimes it occurs as granular aggregates or crusts. Its most characteristic feature is its intense, emerald-green to yellowish-green color. ## Physical Properties Lindgrenite crystals are relatively soft, with a hardness of 4.5 on the Mohs scale. They have a vitreous luster and are most often transparent to translucent. The mineral's density is approximately 4.26 g/cm³. It is brittle, and its crystals should be handled with great care. ## Colors and Varieties Lindgrenite occurs in various shades of green, from light green and yellowish-green to a deep, emerald color. No named varieties are distinguished, and color differences mainly result from crystallization conditions and the presence of possible impurities. ## History and Name The mineral was first described in 1935 by Charles Palache. The name "lindgrenite" was given in honor of Waldemar Lindgren (1860-1939), a prominent Swedish-American geologist and one of the founders of the journal "Economic Geology," who made significant contributions to the study of ore deposits. ## Uses Lindgrenite has no industrial application. It is valued solely as a collector's mineral due to its rarity, attractive color, and well-formed crystals.

Properties

Mohs hardness: 4.5
Color: Green, yellowish green; pale green to yellow-green in transmitted light
Luster: Vitreous
Streak: Pale green
Density: 4.2
Cleavage: On {010}, perfect; on {101} and {100}, very poor.
Fracture: Micaceous
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Lindgrenite can be identified by its characteristic, intense green color, platy crystal habit, and occurrence in association with other secondary copper and molybdenum minerals. Its vitreous luster and pale green streak are also helpful diagnostic features. ## Distinguishing from Similar Minerals Lindgrenite is sometimes confused with other green secondary minerals. It is distinguished from brochantite by its lighter streak and different crystal habit (brochantite forms acicular crystals). It differs from malachite by its lack of reaction with hydrochloric acid (malachite effervesces vigorously) and its habit. Wulfenite, with which it sometimes co-occurs, usually has a different color (yellow, orange) and higher density. ## Crystal Forms Lindgrenite crystals are typically thin, platy, with a hexagonal outline, although they crystallize in the monoclinic system. They often form fan-shaped, rosette-like, or spherulitic aggregates. They also occur as thin crusts on the host rock.

Geological environment

## Genesis Lindgrenite is a secondary mineral, forming in the oxidation (weathering) zones of copper and molybdenum ore deposits. It forms as a result of surface waters acting on primary sulfides, such as chalcopyrite and molybdenite. It is a typical mineral for dry, desert climates. ## Mineral Associations It most commonly co-occurs with other minerals of the oxidation zone, such as molybdenite, powellite, wulfenite, brochantite, antlerite, tenorite, quartz, and also with iron oxides (limonite). ## Localities The most important and type locality (località tipo) is the Chuquicamata mine in the Antofagasta region, Chile, from which the world's best specimens originate. Other known localities include mines in Arizona and Nevada (USA), as well as in Mexico.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those from the Chuquicamata mine in Chile. An ideal specimen should consist of sharp, well-formed, transparent crystals of an intense, emerald-green color, forming aesthetic rosettes or fans on a small rock matrix. Contrast with white or light host rock (e.g., with quartz) significantly enhances visual appeal. ## Popular Localities Undoubtedly, the most sought-after specimens come from the Chuquicamata mine in Chile. They are considered the global standard for this mineral. Specimens from other localities, such as the Inspiration mine in Arizona (USA), are also found in collections but rarely match the quality of Chilean ones.

Care and storage

## Cleaning Lindgrenite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Always thoroughly dry the specimen after cleaning. ## What to Avoid Lindgrenite is sensitive to acids, which can damage or completely dissolve it. Ultrasonic cleaners, chemical agents, and sudden temperature changes should be avoided. The mineral is brittle, so it must be protected from impacts and falls. ## Storage Lindgrenite specimens are best stored in separate, padded collector's boxes to prevent scratches and mechanical damage. They should be protected from dust and moisture. Due to its attractive appearance, it is often displayed in showcases.