Timroseite

Chemical formula: Pb²⁺₂Cu²⁺₅(Te⁶⁺O₆)₂(OH)₂

Timroseite is a very rare lead and copper tellurate, forming microscopic crystals of a characteristic olive-green color.

## Characteristics Timroseite is a lead and copper hydroxytellurate, occurring as very small, bladed or tabular crystals, which rarely exceed 0.2 mm in length. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts on the host rock. Due to their size, individual crystals are usually only visible under magnification. ## Physical Properties This mineral is characterized by a hardness of 2.5 on the Mohs scale, making it relatively soft. Its density is very high, at 6.98 g/cm³. The crystals exhibit a luster ranging from vitreous to slightly greasy. The fracture is uneven. ## Colors and Varieties Timroseite occurs in shades of green, from olive and dark olive to bright, lime green. No named varieties of this mineral have been distinguished. ## History and Name The mineral is named in honor of Timothy "Tim" Rose, an American mineral collector from Southern California, who specialized in minerals from Otto Mountain and was the first to collect specimens of this mineral. Timroseite was approved as a new mineral species by the International Mineralogical Association (IMA) in 2010 (IMA2010-022). It was described by Anthony R. Kampf, Stuart J. Mills, Robert M. Housley, Joseph Marty, and George R. Rossman. ## Uses Timroseite has no industrial application. Its significance is purely scientific and as a collector's item, as a very rare and unique representative of the tellurate group.

Properties

Mohs hardness
2.5
Luster
Vitreous to greasy
Streak
Very pale yellowish green
Density
6.982
Fracture
Irregular/Uneven
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of timroseite is primarily based on its characteristic olive-green to lime-green color, specific occurrence as small, bladed crystals forming rosette-like aggregates, and its association with other rare tellurates. The key is also its locality – this mineral is known only from a few occurrences in the Otto Mountain area in California. Final identification requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Timroseite can be confused with other green secondary minerals, such as brochantite, malachite, or other copper tellurates and tellurites (e.g., ottoite, paratimroseite). Distinguishing it "in the field" is practically impossible. From similar minerals from the same locality, it differs in subtle shades of color, crystal habit (bladed, not acicular, for example), and chemical and structural properties, which can only be examined in a laboratory. ## Crystal Forms Timroseite forms very small, elongated and flattened, bladed crystals. Most often, they occur as radial or rosette-like clusters and aggregates, as well as thin coatings on rock surfaces.

Geological environment

## Genesis Timroseite is a secondary mineral that forms in the oxidation zones (gossans) of low-temperature, hydrothermal ore deposits rich in tellurium. Its formation is associated with the weathering of primary tellurides in the presence of lead and copper minerals. ## Mineral Associations This mineral co-occurs with a number of other, often very rare, secondary minerals. At the type locality, it was found in association with, among others, chalcanthite, anglesite, cerussite, chlorargyrite, quartz, hematite, as well as other tellurates and tellurites, such as ottoite, paratimroseite, markcooperite, dugganite, and xocolatlite. ## Localities Timroseite is an extremely rare mineral, and its occurrence has been confirmed only at a few localities worldwide, situated in one small region. The type locality comprises two adjacent mines: Bird Nest drift and Aga Mine, both on Otto Mountain in San Bernardino County, California, USA. These are the only known localities for this mineral.

Rarity

Very rare

For collectors

## Quality Criteria The quality of timroseite specimens is assessed primarily based on the richness and aesthetics of microcrystal aggregates. Most valued are specimens with clearly formed, rosette-like clusters of intense, lime-green color, contrasting with the darker host rock. Due to the microscopic size of the crystals, their abundance on the specimen's surface is crucial. Purity is not a significant criterion, but the presence of rare associated minerals is important. ## Popular Localities The only source of timroseite specimens are mines located on Otto Mountain in California (USA). Specimens from these localities, especially from the Bird Nest drift, are highly sought after by collectors specializing in rare minerals and "micromounts."

Care and storage

## Cleaning Timroseite specimens are extremely delicate and consist of microscopic crystals. Mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water and any chemicals. ## What to Avoid Ultrasonic cleaners, steam cleaners, acids, solvents, and detergents should be strictly avoided. The mineral is soft and easily susceptible to mechanical damage. Protect it from shocks, scratching, and abrasion. ## Storage Specimens should be stored exclusively in sealed, padded "micromount" boxes to protect them from dust and physical damage. Do not expose them to direct sunlight or sudden temperature changes.

External references

Sources

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