Earlshannonite

Chemical formula: Mn²⁺Fe³⁺₂(PO₄)₂(OH)₂·4H₂O

Earlshannonite is a rare hydrated manganese iron phosphate, forming aggregates of small, bladed, brown crystals.

## Characteristics Earlshannonite is a rare mineral from the phosphate group, chemically classified as a hydrated manganese iron phosphate. It occurs as aggregates of small, bladed or thin, tabular crystals, which rarely exceed 1 mm in length. These crystals often form rosette-like or radial aggregates, as well as spherulitic (spherical) forms. Its appearance is distinctive, although due to the small size of the crystals, magnification is often required for observation. ## Physical Properties This mineral is characterized by a vitreous luster. It is translucent. Its Mohs hardness is 3, and its density is approximately 3.06 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties Earlshannonite is typically reddish-brown to dark brown. The streak, which is the color of the powdered mineral, is light brown. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was named in honor of Earl V. Shannon (1895–1925), an American chemist and mineralogist who worked as an assistant curator at the National Museum of Natural History in Washington (part of the Smithsonian Institution). The mineral was first described in 1985 based on samples from the Foote Lithium Co. mine in the Kings Mountain area, North Carolina, USA. ## Uses Due to its rarity and small crystal size, earlshannonite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or phosphate minerals.

Properties

Mohs hardness
3-4
Color
Dark reddish brown, yellowish brown, yellow-orange, bright yellow
Luster
Vitreous
Streak
Light brown
Density
2.90
Cleavage
Two poor cleavages, one is likely {100}.
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Earlshannonite can be identified by its characteristic bladed crystals forming radial or rosette-like aggregates. Its brown color, vitreous luster, and occurrence in granitic pegmatites are key features. However, definitive identification requires advanced research methods, such as chemical analysis (EDS) or X-ray diffraction (XRD), due to its similarity to other phosphates. ## Differentiation from Similar Minerals This mineral can be confused with other secondary iron and manganese phosphates, such as strengite, rockbridgeite, or ludlamite, which may occur in similar environments. Distinguishing it based on visual features is difficult and often impossible without specialized equipment. Earlshannonite is characterized by its specific crystal habit (thin blades) and chemical composition. ## Crystal Forms Crystals are thin, bladed, elongated in one direction, and flattened. They usually form radial, rosette-like, or spherulitic aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Earlshannonite is a secondary phosphate mineral that forms in complex granitic pegmatites, rich in lithium and phosphorus. It originates from hydrothermal alteration or weathering of primary phosphates, such as triphylite, in the presence of iron- and manganese-rich solutions. ## Mineral Associations It co-occurs with other phosphate minerals, such as strengite, rockbridgeite, laueite, stewartite, as well as with quartz, microcline, and albite, which constitute the host rock (pegmatite). ## Localities The most important and well-documented occurrences of this mineral worldwide include: - Foote Lithium Co. mine in Kings Mountain, North Carolina, USA (type locality). - Tip Top Mine, near Custer, South Dakota, USA. - Localities in the Hagendorf-Süd region, Bavaria, Germany. - Palermo No. 1 Mine, Grafton County, New Hampshire, USA.

Rarity

Rare

For collectors

## Quality Criteria For collectors, specimens with clearly formed, radial or rosette-like crystal aggregates are most valuable. An intense, reddish-brown color and good contrast with matrix minerals, such as white albite or quartz, are highly prized. The size of the aggregates is also important, although they rarely exceed a few millimeters in diameter. ## Popular Localities The most valued specimens come from classic US localities, namely the Foote mine in North Carolina and Tip Top in South Dakota. Specimens from these locations are considered benchmark examples for this mineral species.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and perfect cleavage, ultrasonic cleaners and vigorous scrubbing should be avoided. If liquid is necessary, distilled water is recommended. ## What to Avoid Avoid contact with acids and other aggressive chemicals that can damage the mineral. Earlshannonite is a hydrated mineral, so it should not be heated, as this can lead to the loss of structural water and its destruction. Prolonged exposure to moisture is also not advisable. ## Storage Specimens should be stored in stable conditions, away from dust and direct sunlight. It is best to place them in a closed display box to protect delicate crystals from mechanical damage.

External references

Sources

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