Retzian-(Ce)

Chemical formula: Mn₂+₂Ce₃+As₅+O₄(OH)₄

Retzian-(Ce) is a rare manganese and cerium arsenate, forming small, prismatic crystals with a characteristic reddish-brown color.

## Characteristics Retzian-(Ce) is a mineral from the arsenate group, belonging to the retzian group. Cerium dominates its structure as a rare earth element, which is indicated in its name. It forms elongated, prismatic or acicular crystals, often gathered in radial or acicular aggregates, as well as spherical or reniform shapes. Crystals are usually small, rarely exceeding a few millimeters in length. Its color ranges from reddish-brown to dark brown, sometimes with a yellowish or orange tint. ## Physical Properties This mineral is characterized by a Mohs hardness of 4 and a density of approximately 4.16 g/cm³. It exhibits a luster ranging from vitreous to resinous. It is a brittle mineral with an uneven fracture. It is translucent to opaque, and its streak is light yellow to light brown. ## Colors and Varieties The predominant color of retzian-(Ce) is reddish-brown to dark brown. No distinct color or commercial varieties are recognized. ## History and Name The name "retzian" was given in honor of the Swedish chemist and naturalist Anders Johan Retzius (1742-1821). The suffix "-(Ce)" indicates the dominance of cerium among the rare earth elements in the mineral's chemical composition, in accordance with IMA nomenclature. The mineral was first described in the Moss mine in Nordmark (Sweden).

Properties

Mohs hardness: 4
Luster: Vitreous to Resinous
Streak: Light yellow to light brown
Density: 4.16
Cleavage: Good on {101}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Characteristic features of retzian-(Ce) include its reddish-brown color, prismatic or acicular crystal habit, often forming radial aggregates, and its mineral association. Vitreous to resinous luster and relatively low hardness (4 on the Mohs scale) are also helpful in identification. ## Differentiation from Similar Minerals Retzian-(Ce) can be confused with other minerals from the retzian group, such as retzian-(La) or retzian-(Nd). Distinguishing them requires advanced chemical analyses (e.g., EDS) to determine the dominant rare earth element. It may also resemble some tourmalines or piemontite, but differs from them in hardness, crystal habit, and occurrence environment. ## Crystal Forms Crystals are usually elongated along the c-axis, with a prismatic or acicular habit. They often occur as radial or fan-shaped aggregates. Spherical and reniform aggregates with a radial structure are also found.

Geological environment

## Genesis Retzian-(Ce) is a secondary mineral, formed in hydrothermal veins or as a result of the metamorphism of manganese and iron ore deposits. It forms in environments rich in arsenic and rare earth elements. ## Mineral Associations It often co-occurs with other manganese and arsenic minerals. Typical associated minerals include hausmannite, magnetite, tephroite, pyrochroite, sarkinite, brandtite, as well as calcite and barite. ## Localities The most important and classic localities for this mineral are in Sweden, in the Filipstad region (Värmland), especially in the Långban, Nordmark, and Moss mines. It is also known from Franklin, New Jersey (USA), the Gozaisho mine in Japan, and the Valgraveglia mine in Italy.

Rarity

Rare

For collectors

## Quality Criteria The most valuable retzian-(Ce) specimens are those with well-formed, sharp, and undamaged crystals of intense, reddish-brown color. Radial aggregates of crystals ("sunbursts") on a contrasting rock matrix are particularly prized. Crystal size and aesthetic composition significantly increase the specimen's value. ## Popular Localities Specimens from the Swedish mines in Långban and Nordmark are considered the best in the world. These localities yield classic, well-formed crystals that serve as a benchmark for this mineral.

Care and storage

## Cleaning Due to its brittleness and rarity, specimens should be cleaned very carefully. The safest method is to use compressed air to remove dust. If wet cleaning is necessary, use a soft-bristled brush and distilled water, then dry the specimen thoroughly. ## What to Avoid Avoid contact with acids and other chemicals that may react with arsenates. Ultrasonic cleaners should not be used, as they could damage the fragile crystals. The mineral is sensitive to impacts and shocks. ## Storage Retzian-(Ce) specimens should be stored in separate, padded boxes to prevent abrasion and mechanical damage. They should be protected from dust and moisture. Due to its arsenic content, it is recommended to wash hands after handling the mineral.

Sources

IMA Mineral List (CNMNC)