Raadeite

Chemical formula: Mg<sub>7</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>8</sub>

Raadeite is a very rare basic magnesium phosphate, forming colorless, bladed crystals and rosetted aggregates.

## Characteristics Raadeite is a hydrated basic magnesium phosphate. It occurs as small, colorless, bladed or acicular crystals, which often form radial or rosetted aggregates. Individual crystals rarely exceed 1 mm in length. It is a transparent mineral with a vitreous luster. ## Physical Properties This mineral is characterized by a Mohs hardness of 4. Its density is calculated at 2.85 g/cm³. The crystals exhibit perfect cleavage in one direction. ## History and Name Raadeite was first described in 2008 by Gunnar Raade, Muriel Erambert, Peter B. Williams, and Werner H. Paar. The mineral is named in honor of Gunnar Raade (b. 1944), a Norwegian mineralogist and curator of the mineral collection at the University of Oslo, for his contributions to the mineralogy of phosphates from the Modum complex in Norway.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
White
Density
2.85
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Key diagnostic features include its specific form – radial aggregates composed of colorless, bladed crystals. Its occurrence in serpentinites in association with albite, enstatite, and other magnesium phosphates is also a strong indicator. ## Distinguishing from similar minerals It can be confused with other colorless, acicular secondary minerals. It differs from talc by its higher hardness and crystal form. Identification requires advanced analytical methods such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). ## Crystal forms It forms elongated, bladed crystals, flattened parallel to {100} and elongated along [001]. These crystals group into characteristic, rosetted or radial aggregates.

Geological environment

## Genesis Raadeite is a secondary mineral, formed by hydrothermal processes in serpentinites. In its type locality (Tingelstadtjern, Norway), it formed as a result of metasomatic alteration of dunite, in the contact zone with granitic pegmatites. ## Mineral associations It most commonly co-occurs with albite, enstatite, magnesite, clinochlore, holtedahlite, satterlyite, olmsteadite, and apatite. ## Localities The only confirmed and described locality for raadeite in the world is the Tingelstadtjern serpentinite quarry in the municipality of Modum, Buskerud county, Norway.

Rarity

Extremely rare

For collectors

## Quality criteria As a "micromount" type mineral, specimens with well-formed, sharp, and clearly defined rosetted crystal aggregates are most highly valued. Aesthetic composition on the matrix and the absence of damage to the delicate acicular crystals are also important. Contrast with a dark matrix rock (serpentinite) enhances visual appeal.

Care and storage

## Cleaning Due to its rarity and delicacy, cleaning should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. Avoid contact with water and any chemical agents. ## What to avoid Avoid ultrasonics, steam cleaning, acids, and detergents. The mineral is sensitive to shocks and impacts due to its perfect cleavage. Store away from heat sources. ## Storage Raadeite specimens should be stored in stable conditions, preferably in a sealed "micromount" box, to protect them from dust, mechanical damage, and sudden changes in humidity.

Sources

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