Keckite

Chemical formula: CaMn<sup>2+</sup>(Fe<sup>3+</sup>,Mn<sup>2+</sup>)<sub>2</sub>Fe<sup>3+</sup><sub>2</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>3</sub>·7H<sub>2</sub>O

Keckite is a rare, hydrated calcium, manganese, and iron phosphate, forming characteristic radial aggregates of small, acicular brown crystals.

## Characteristics Keckite is a mineral from the phosphate group, visually manifesting as clusters of small, acicular or bladed crystals. These crystals often form radial, spherical, or hemispherical aggregates, resembling small hedgehogs or fans. Individual needles are very thin and elongated, and their clusters rarely exceed a few millimeters in diameter. Due to its delicate structure, keckite specimens are brittle. ## Physical Properties This mineral is characterized by a silky luster on crystal surfaces. It is translucent, and its Mohs hardness is approximately 3, classifying it as a relatively soft mineral. The density of keckite is calculated at 2.91 g/cm³. ## Colors and Varieties Keckite occurs in shades of brown – from yellowish-brown and reddish-brown to dark brown. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral's name honors Erich Keck (1933-2019), an Austrian mineral collector from Linz, who specialized in pegmatite minerals and was the first to find this mineral. Keckite was described as a new mineral species in 1979 by Paul B. Moore, Anthony R. Kampf, and Anthony J. Irving based on samples from the type locality in Hagendorf-Süd, Bavaria. ## Uses Keckite has no industrial application. It is solely a mineral of scientific and collecting interest, sought after by advanced collectors of rare phosphates.

Properties

Mohs hardness
3
Luster
Silky
Streak
Yellowish-brown
Density
2.91
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification A characteristic feature of keckite is its radial aggregates composed of very fine, acicular or bladed crystals of brown color and silky luster. It occurs in cavities in phosphate rocks, often on other minerals. ## Distinguishing from Similar Minerals Keckite can be confused with other rare phosphates of similar appearance, such as rockbridgeite, frondelite, or strengite. Distinguishing it based on visual characteristics is very difficult and usually requires advanced chemical (EDS) or X-ray (XRD) analyses. The mineralogical context, i.e., co-occurrence with other phosphates from Hagendorf or Palermo, can be an important clue. ## Crystal Forms Keckite crystals are strongly elongated, acicular, or bladed. They usually form radial, spherical, or hemispherical aggregates. Single, well-formed crystals are extremely rare and microscopic in size.

Geological environment

## Genesis Keckite is a secondary phosphate mineral. It forms as a result of hydrothermal alteration or weathering of primary phosphates (mainly zwickerite and triphylite) in granitic pegmatites. It forms in the late stage of crystallization, filling small cavities and fissures in massive phosphate rocks. ## Mineral Associations This mineral co-occurs with other phosphates, such as rockbridgeite, strengite, phosphosiderite, zwickerite, laueite, stewartite, jahnsite-(CaMnFe), and apatite. ## Localities The most important and classic localities for this mineral are phosphate pegmatites. The type locality is the Hagendorf-Süd quarry in Waidhaus, Upper Palatinate, Bavaria, Germany. Another known occurrence is the Palermo No. 1 mine in Groton, Grafton County, New Hampshire, USA. These are the only confirmed localities providing well-identified specimens.

Rarity

Very rare

For collectors

## Quality Criteria The most prized keckite specimens are those with well-defined, spherical or radial aggregates of intense brown color, contrasting with the light background of the matrix rock. The size of the aggregates and the absence of damage to the delicate crystals are important. Due to the microscopic nature of the mineral, specimens are primarily evaluated under magnification. ## Popular Localities Specimens from the type locality – Hagendorf-Süd in Germany – are by far the most sought after by collectors. Material from the Palermo mine in the USA is also valued, but less commonly found on the market.

Care and storage

## Cleaning Keckite specimens are extremely delicate and brittle. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used from a safe distance to remove loose dust. Contact with water and any brushes that could damage the small, acicular crystals should be avoided. ## What to Avoid Ultrasonic cleaners, chemicals, acids, and detergents should be absolutely avoided. The mineral is sensitive to shocks and impacts. It should not be exposed to high temperatures or prolonged moisture. ## Storage Keckite requires storage under stable conditions, preferably in a sealed "micromount" box that protects it from dust, shocks, and mechanical damage. It should not be stored loosely with other, harder minerals.

Sources

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