Planerite

Chemical formula: Al₆(PO₄)₂(PO₃OH)₂(OH)₈·₄H₂O

Planerite is a rare mineral from the phosphate group, forming spherical aggregates and crusts with a characteristic greenish-blue color.

## Characteristics Planerite is a hydrated aluminum phosphate, closely related to turquoise. It most often occurs in the form of small, spherical or reniform aggregates with a radial structure, as well as crusts and veins. Single, well-formed crystals are extremely rare and appear as small, tabular or bladed forms, usually not exceeding 1 mm in length. Due to its structure and chemical composition, planerite is a member of the turquoise group. ## Physical properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. Its luster is most often earthy or dull in the case of massive aggregates, and vitreous on the faces of rare microcrystals. It is a relatively light mineral, with a density of about 2.68 g/cm³. It is opaque, only translucent on thin edges. ## Colors and varieties Planerite ranges in color from green, through greenish-blue, to bluish-green. White or yellowish specimens are also found. The intensity and shade of color depend on chemical impurities, mainly copper. No named varieties are distinguished, although it is sometimes confused with turquoise or wavellite due to similarities in color and mode of occurrence. ## History and name The mineral's name comes from the surname of Dmitry Ivanovich Planer (1822–1883), a Russian mineralogist who first collected and described its specimens. The mineral was formally described by Nikolai Ivanovich Koksharov in 1862. The type locality (locus typicus) is Gumeshevskaya Mountain near Sysert in the Ural Mountains, Russia. ## Uses Planerite has no industrial application. Its significance is purely scientific and collectible. It is sought after by collectors specializing in rare minerals or phosphate group minerals.

Properties

Mohs hardness: 5
Luster: Earthy
Streak: White to greenish-white
Density: 2.68
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Triclinic

Diagnostic features

## Identification Planerite is most easily recognized by its characteristic mode of occurrence – spherical or reniform aggregates with a radial internal structure. Its greenish-blue color is also key. Unlike many similar minerals, it does not react with cold hydrochloric acid. ## Distinguishing from similar minerals Planerite is often confused with turquoise, wavellite, or variscite. It is usually lighter and has a more greenish hue than turquoise, and is also lighter in weight. Wavellite, although forming similar spherical aggregates, usually has a lower hardness (3.5-4) and often exhibits a more vitreous luster on fracture. Variscite also forms similar aggregates, but usually has a pure green color, without bluish tints. ## Crystal forms Well-formed crystals are extremely rare and appear as small, tabular or bladed forms, often grouped into rosette-like aggregates. The dominant and most typical forms of occurrence are spherical, radial aggregates (spherulites), botryoidal aggregates, reniform aggregates, and massive crusts.

Geological environment

## Genesis Planerite is a secondary mineral, formed in the oxidation (weathering) zones of ore deposits, as well as in sedimentary rocks rich in phosphorus and aluminum. It forms as a result of the action of low-temperature hydrothermal solutions or surface waters on aluminous rocks, often in the presence of apatite or other primary phosphate minerals. ## Mineral associations This mineral often co-occurs with other phosphates, such as turquoise, wavellite, and variscite. It is also accompanied by quartz, limonite, kaolinite, gibbsite, and minerals from the mica group. ## Localities The most important historical locality, which is also the type locality, is the Gumeshevskoye mine in the Ural Mountains, Russia. Other known localities include the General Trimble mine in Chester County, Pennsylvania (USA), the National Belle mine in Ouray, Colorado (USA), and the Kapunda area in South Australia. Occurrences have also been reported in Germany (Saxony) and Austria (Styria).

Rarity

Rare

For collectors

## Quality criteria The most valued by collectors are specimens with well-formed, spherical aggregates of intense, greenish-blue color. The absence of damage to delicate spherulites and aesthetic placement on the matrix rock are important. Specimens from historical, classic localities, such as the Urals or Pennsylvania, are particularly sought after. Extremely rare, visible-to-the-naked-eye crystals, even small ones, fetch very high prices due to their uniqueness. ## Popular localities The historical localities in Russia (Urals) and the USA (Pennsylvania, Colorado) are considered the best for this mineral. Specimens from these localities are regarded as classics and adorn advanced systematic mineral collections.

Care and storage

## Cleaning Planerite specimens should be cleaned very carefully. It is best to use a soft brush to remove dust. If necessary, compressed air can be used. If washing is essential, use a small amount of distilled water and immediately dry the specimen thoroughly. Ultrasonic cleaners should be avoided. ## What to avoid Planerite is sensitive to chemicals, especially acids, which can damage it. It should be protected from prolonged exposure to strong sunlight, which can cause color fading. High temperatures and sudden thermal changes should also be avoided. As a hydrated mineral, it is sensitive to dehydration, which can lead to cracking. ## Storage Planerite specimens are best stored in closed, stable conditions, away from dust and direct light. It is advisable to place them in separate boxes or on a soft surface to avoid abrasions and mechanical damage, especially in the case of delicate, spherical aggregates.

Sources

IMA Mineral List (CNMNC)