Ulrichite

Chemical formula: CaCu²⁺(U⁶⁺O₂)(PO₄)₂·₄H₂O

Ulrichite is a rare, hydrated uranyl, calcium, and copper phosphate, forming characteristic apple-green crystals and aggregates.

## Characteristics Ulrichite is a secondary mineral from the uranyl phosphate group, prized by collectors for its intense, apple-green color. It occurs as small, tabular or bladed crystals, which often form radial, rosette-like, or spherulitic aggregates. Individual crystals rarely exceed 1 mm in length, but their clusters can reach several millimeters in diameter, creating striking reniform or spherical forms on the surface of the host rock. ## Physical Properties This mineral is characterized by a hardness of 3-3.5 on the Mohs scale, making it relatively soft and brittle. It has a vitreous luster and is transparent to translucent. Its density has not been precisely measured but is estimated based on its chemical composition. ## Colors and Varieties Ulrichite occurs in characteristic shades of green, from apple-green to lime-green. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was discovered and described in 1988. Its name honors George H. F. Ulrich (1830-1900), a German-Australian mineralogist and geologist who made significant contributions to the geological surveys of Victoria, Australia, where ulrichite was first found. ## Uses Due to its rarity, small crystal size, and uranium content, ulrichite has no industrial applications. It is solely an object of interest for collectors specializing in uranium minerals and rare phosphates.

Properties

Mohs hardness: 3-3.5
Luster: Vitreous
Streak: White
Density: 0
Transparency: Transparent,Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features of ulrichite include its intense, apple-green color, characteristic forms of occurrence (radial aggregates, rosettes, spherulites), and vitreous luster. The mineral exhibits strong, green fluorescence under ultraviolet light (both shortwave and longwave), which is very helpful for identification. ## Distinguishing from Similar Minerals Ulrichite can be confused with other green secondary uranium minerals, such as torbernite, metatorbernite, or autunite. It is distinguished from torbernite by its monoclinic crystal system (torbernite is tetragonal) and often radial habit. However, this requires advanced analysis (e.g., XRD). In collecting practice, verifying the specimen's locality of origin is crucial. ## Crystal Forms Ulrichite crystals are most often tabular, flattened, with an outline resembling a rectangle or hexagon. They usually occur in radial, fan-shaped, or spherical clusters (spherulites), forming crusts on the rock.

Geological environment

## Genesis Ulrichite is a secondary mineral, forming in the oxidation (weathering) zone of deposits containing uraninite. It forms in voids and fractures in granitic rocks, as a result of phosphate-rich solutions acting on primary uranium minerals, in the presence of copper and calcium ions. ## Mineral Associations This mineral often co-occurs with other secondary uranium minerals. At the type locality (Lake Boga), it was found in association with cyrton (a variety of zircon), fluorapatite, libethenite, torbernite, saleeite, and wavellite. ## Localities The most important and type locality for ulrichite is the Lake Boga granite quarry in Victoria, Australia. This is the only confirmed locality from which well-formed, identifiable specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The most prized ulrichite specimens are characterized by an intense, vivid, apple-green color. Well-formed, radial aggregates and rosettes that stand out clearly from the host rock (matrix) are highly valued. The size of the clusters is also important – the larger and more complete, the higher the specimen's value. The absence of mechanical damage is crucial due to the mineral's high brittleness. ## Popular Localities The only source of valuable collector specimens is the type locality – the Lake Boga quarry in Australia. Specimens from this location are considered classic for this species and are most desired by collectors of uranium minerals.

Care and storage

## Cleaning Ulrichite specimens are very delicate and brittle. Cleaning should be kept to an absolute minimum. If necessary, a soft brush can be used to remove dust or compressed air from a safe distance. Avoid contact with water, which can damage the mineral. ## What to Avoid Ulrichite is sensitive to chemicals, especially acids. Ultrasonic cleaners, sudden temperature changes, and direct, prolonged exposure to sunlight, which can cause color fading, should be avoided. As a hydrated mineral, it is sensitive to changes in humidity and high temperatures, which can lead to its dehydration and destruction. ## Storage Specimens should be stored in stable conditions, in closed, padded boxes or display cases, away from sources of heat, light, and moisture. Due to its brittleness, it should be protected from vibrations and impacts. As a uranium-bearing mineral, it emits ionizing radiation – it should be stored away from other radiation-sensitive minerals and direct contact should be limited.