Plimerite

Chemical formula: Zn<sup>2+</sup><sub>2</sub>Fe<sup>3+</sup><sub>3</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)<sub>4</sub>(H<sub>2</sub>O)

Plimerite is a very rare secondary zinc and iron phosphate, forming characteristic spherical brown aggregates.

## Characteristics Plimerite is a hydrated zinc and iron phosphate belonging to the rockbridgeite group. It occurs as small, spherical or reniform (botryoidal) aggregates, rarely exceeding a few millimeters in diameter. These aggregates have a radial-fibrous structure, which is sometimes visible on fractured surfaces. It is usually opaque, although thin splinters may be translucent. Its surface has a luster ranging from vitreous to resinous. ## Physical Properties The hardness of plimerite on the Mohs scale is 4-5, making it a medium-hard mineral. Its density is calculated to be approximately 3.65 g/cm³. It does not exhibit cleavage but may show parting parallel to the basal plane of the crystal. ## Colors and Varieties This mineral has a characteristic color palette, ranging from yellowish-brown, through reddish-brown, to dark brown. No color or commercial varieties have been distinguished. ## History and Name Plimerite was recognized as a new mineral by the International Mineralogical Association (IMA) in 2008. Its name honors Ian Rutherfurd Plimer (born 1946), an Australian professor of geology and author of many works on the Broken Hill deposit, where this mineral was discovered. The type locality is the Kintore Opencut in Broken Hill, New South Wales, Australia. ## Uses Due to its extreme rarity, plimerite has no industrial application. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness
4-5
Luster
Vitreous to resinous
Streak
Yellow-brown
Density
3.65
Cleavage
None
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Trigonal

Diagnostic features

## Identification Characteristic features of plimerite include its occurrence as small, brown spheres (botryoidal aggregates), its radial internal structure, and its vitreous to resinous luster. Its origin from the only known locality – Broken Hill – and its association with other rare phosphates are also crucial for identification. ## Distinguishing from Similar Minerals Plimerite can be confused with other brown minerals of similar habit, such as goethite or other phosphates from the rockbridgeite group. Goethite has a similar color and form but usually a more dull or earthy luster and a different streak. Distinguishing it from other phosphates (e.g., rockbridgeite) is very difficult visually and usually requires advanced chemical analyses (EDS). ## Crystal Forms Plimerite does not form well-developed, macroscopically visible crystals. It occurs exclusively in the form of spherical, botryoidal, and reniform aggregates, which consist of tightly packed, radially arranged fibers.

Geological environment

## Genesis Plimerite is a secondary mineral, forming in the oxidation zone (gossan) of polymetallic sulfide deposits. It crystallizes from solutions rich in phosphorus, zinc, and iron, which resulted from the weathering and decomposition of primary ore minerals (e.g., sphalerite) and surrounding rocks. ## Mineral Associations This mineral occurs in association with other secondary phosphates and oxides, such as scholzite, phosphosiderite, strengite, libethenite, rockbridgeite, goethite, as well as with quartz and coronadite. ## Localities The only confirmed occurrence of plimerite in the world is the Kintore Opencut in the Broken Hill area, New South Wales, Australia. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria The most prized plimerite specimens are those that exhibit well-formed, undamaged spherical aggregates of intense brown color. Samples in which the spherical plimerite aggregates clearly stand out from the matrix are highly valued. Association with other rare and aesthetic secondary minerals from Broken Hill adds additional value. ## Popular Localities All specimens available on the collector's market come from a single location – the Broken Hill mine in Australia. This makes this mineral extremely sought after by collectors specializing in rare species and minerals from this classic locality.

Care and storage

## Cleaning Plimerite specimens should only be dry-cleaned, using a soft brush to remove dust. Contact with water, especially tap water, is not recommended. If necessary, a minimal amount of distilled water can be used, and the specimen should be immediately dried with compressed air or allowed to dry quickly. ## What to Avoid All chemical agents, especially acids, which can destroy the mineral, should be avoided. Cleaning in ultrasonic cleaners is not recommended. The mineral is stable, but it should be protected from prolonged exposure to moisture and extreme temperatures. ## Storage It is recommended to store specimens in closed "micromount" boxes or display cases to protect them from dust and mechanical damage. Avoid exposure to direct sunlight, which could theoretically affect its color.

External references

Sources

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