Perhamite

Chemical formula: Ca<sub>3</sub>Al<sub>7.7</sub>Si<sub>3</sub>P<sub>4</sub>O<sub>23.5</sub>(OH)<sub>14.1</sub>·8H<sub>2</sub>O

A rare aluminum and calcium phosphate, forming characteristic white aggregates with a silky or pearly luster, resembling compressed fibers.

## Characteristics Perhamite is a hydrated aluminum and calcium phosphate, most commonly found in the form of radiating or spherulitic aggregates. These consist of tiny, lath-like or platy crystals that together form compact, felt-like masses. Individual crystals are rarely visible to the naked eye. Specimens typically have a white color and a characteristic luster, ranging from silky to pearly on cleavage surfaces. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 5. It is light, with a density close to 2.55 g/cm³. The crystals exhibit perfect cleavage in one direction, which, combined with their small size, contributes to the fibrous appearance of the aggregates. The luster is usually pearly or silky, and the mineral is translucent. ## Colors and Varieties Perhamite is a mineral with uniform coloration. It occurs almost exclusively in white, sometimes with a creamy tint. No colored varieties or trade names are distinguished for it. ## History and Name The mineral was first described in 1977 by P.J. Dunn and D.E. Appleman. The name honors Frank C. Perham (born 1934), an American miner and mineral collector from Maine, who discovered the first specimens of this mineral in the Bell Pit pegmatite in Newry. ## Uses Perhamite has no industrial applications. Its significance is limited to scientific and collecting interest as a rare and structurally interesting mineral.

Properties

Mohs hardness
5
Luster
Pearly, Silky
Streak
White
Density
2.55
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Perhamite is most easily recognized by its characteristic mode of occurrence – white, radiating or spherical aggregates with a silky or pearly luster. The appearance resembling compressed fibers or felt is very typical. Perfect cleavage in one direction is visible on individual lamellae under magnification. ## Distinguishing from Similar Minerals Perhamite is sometimes confused with other white phosphate minerals that form radiating aggregates, such as wavellite or wardite. Wavellite usually forms more vitreous and more clearly defined spherulites. Wardite is harder (7) and has a vitreous luster. Accurate differentiation often requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Perhamite crystals are very small, tabular or lath-like, with a hexagonal outline. They almost always occur in the form of radiating, spherulitic, or rosette-like aggregates. Single, well-formed crystals are rarely observed.

Geological environment

## Genesis Perhamite is a secondary mineral, forming in hydrothermal zones or as a result of post-magmatic processes in complex granitic pegmatites rich in phosphates. It forms in rock cavities and fissures, often as one of the later crystallization products. ## Mineral Associations This mineral co-occurs with other phosphates typical of pegmatites. In its type locality (Bell Pit, Maine, USA), it was found in association with eosphorite, siderite, quartz, albite, and apatite. In other localities, it is accompanied by, among others, wardite, crandallite, wavellite, and brazilianite. ## Localities The most important and historically first locality is the Bell Pit in Newry, Oxford County, Maine (USA). Other known localities include the Silver Coin mine in Valmy, Humboldt County (Nevada, USA), and pegmatites in the Minas Gerais region in Brazil.

Rarity

Rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, spherical or radiating aggregates of pure white color and a distinct, silky luster. Contrast with the rock matrix and the absence of damage to delicate structures are important. Specimens from the type locality (Newry, Maine) are particularly sought after due to their historical significance. ## Popular Localities Definitely the most desired are classic specimens from the Bell Pit in Newry, Maine, USA. Good quality aggregates also come from the Silver Coin mine in Nevada, USA.

Care and storage

## Cleaning Perhamite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its softness and potential reactivity, avoid washing it in water, especially with detergents. If it is necessary to remove loose contaminants, compressed air can be used from a safe distance. ## What to Avoid Avoid contact with all chemicals, including acids and strong bases, which can damage the mineral. Perhamite is soft and brittle, so it must be protected from impacts, scratches, and vibrations. It should not be heated or exposed to prolonged moisture. ## Storage It is recommended to store specimens in separate, padded collector boxes to prevent abrasions and mechanical damage. Keep it away from harder minerals. Store in stable conditions, away from sources of moisture and extreme temperatures.

External references

Sources

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