Retzian-(Nd)

Chemical formula: Mn²⁺₂NdAs⁵⁺O₄(OH)₄

A rare manganese and neodymium arsenate, forming small, radial aggregates of a reddish-brown color.

## Characteristics Retzian-(Nd) is a rare mineral from the arsenate group, chemically classified as a basic manganese and neodymium arsenate. It occurs as small, acicular or prismatic crystals, which most often form radial, spherical, or fan-shaped aggregates. Individual crystals rarely exceed 1-2 mm in length. Its characteristic feature is an intense, reddish-brown to brown color. ## Physical Properties Crystals exhibit a vitreous to greasy luster. The mineral is translucent to opaque. Its Mohs hardness is approximately 4, and its density is approximately 4.16 g/cm³. It has distinct cleavage in one direction. ## Colors and Varieties This mineral occurs in uniform shades from reddish-brown to dark brown. No color or commercial varieties are distinguished. ## History and Name The name "retzian" was given in 1894 by Hjalmar Sjögren in honor of the Swedish chemist and botanist Anders Johan Retzius (1742-1821). The suffix "-(Nd)" was added later, in accordance with the naming rules for rare earth minerals, to indicate neodymium (Nd) as the dominant rare earth element in this particular member of the series. The mineral was originally described from samples from the Långban deposit in Sweden. ## Applications Retzian-(Nd) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from skarn deposits, as well as scientists studying the mineralogy of arsenates and rare earth elements.

Properties

Mohs hardness
3-4
Color
Pinkish brown to dark reddish brown
Luster
Vitreous to greasy
Streak
Very light brown
Density
3.77
Cleavage
Distinct on {100}
Fracture
Irregular/Uneven,Sub-Conchoidal
Transparency
Transparent,Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Characteristic features of retzian-(Nd) include its reddish-brown color, radial or fan-shaped aggregates composed of small, acicular crystals, and its occurrence in a specific geological environment – metamorphic manganese deposits. ## Distinguishing from Similar Minerals Retzian-(Nd) can be confused with other minerals from the retzian group, such as retzian-(Ce) and retzian-(La). Distinguishing them requires advanced chemical analyses (e.g., EDS) to determine the dominant rare earth element. Visually, it may resemble some zeolites or other arsenates, but its mineral paragenesis is a key diagnostic clue. ## Crystal Forms It forms elongated, prismatic, or acicular crystals, almost always gathered in radial, spherical, or fan-shaped aggregates. Single, well-formed crystals are rarely found.

Geological environment

## Genesis Retzian-(Nd) is a secondary mineral, formed in iron and manganese ore deposits that have undergone contact and regional metamorphism. It forms in fissures and cavities in skarn rocks and dolomites. ## Mineral Associations It most often co-occurs with other rare minerals from metamorphic deposits, such as jacobsite, hausmannite, magnetite, dolomite, calcite, pyrochroite, brandtite, sarkinite, as well as other arsenates and rare earth minerals. ## Localities The most important and classic locality for this mineral is the Långban mine in the Värmland region of Sweden. It is also known from several other localities worldwide, including the Sterling Hill deposit in Ogdensburg (New Jersey, USA) and the Gozaisho mine in Fukushima Prefecture, Japan.

Rarity

Very rare

For collectors

## Quality Criteria Specimens most valued by collectors are those with well-formed, radial aggregates of an intense, reddish-brown color, contrasting with a light rock matrix (e.g., white dolomite). The size of the aggregates and the absence of mechanical damage significantly increase the value of the specimen. Due to the rarity of the mineral, even microscopic but well-formed examples are considered valuable. ## Popular Localities By far the most desired and classic specimens come from the type locality – Långban in Sweden. Material from this mine is considered exemplary for this mineral species.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft brush to remove dust. Due to its rarity and potential fragility, washing in water, especially in ultrasonic cleaners, should be avoided. ## What to Avoid Contact with any chemicals, particularly acids, which can damage it, should be avoided. The mineral is brittle and sensitive to impact. It should not be heated or exposed to prolonged strong light. ## Storage Retzian-(Nd) specimens are best stored under stable conditions, in closed display boxes, to protect them from dust, mechanical damage, and sudden temperature changes. Due to the small size of the crystals, it often occurs on a delicate rock matrix, which also requires careful handling.

External references

Sources

Read more