Siudaite

Chemical formula: Na₈(Mn₂+₂Na)Ca₆Fe₃+₃Zr₄+₃Nb₅+Si₂₅O₇₄(OH)₂Cl·₅H₂O

Siudaite is an extremely rare mineral from the eudialyte group, discovered in Chile, with a complex structure and a brownish-red color.

## Characteristics Siudaite is a complex cyclosilicate belonging to the eudialyte group. It has been identified as single, anhedral (irregularly shaped) grains up to 1.5 mm in size, intergrown with other minerals. Its appearance is inconspicuous, and the grains are brittle and lack distinct crystal faces. ## Physical Properties The mineral has a hardness of approximately 5 on the Mohs scale. It exhibits a vitreous luster and is translucent. The density calculated from the formula and cell parameters is 2.96 g/cm³. ## Colors and Varieties Siudaite is brownish-red in color. Neither pleochroism nor any varieties have been observed. ## History and Name The mineral is named in honor of Professor Rafał Siuda (born 1975), a Polish mineralogist and geochemist from the University of Warsaw, in recognition of his contributions to the study of minerals from the eudialyte group. Siudaite was approved as a new mineral by the International Mineralogical Association (IMA) in 2018 (number 2018-137). It was described by a research team led by Bożena Łasocha based on material collected from the San Gabriel mine in Chile. ## Uses Due to its extreme rarity and microscopic size, siudaite has no practical or commercial applications. It is of purely scientific significance and is an object of interest for specialized collectors of rare minerals.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 2.96
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of siudaite is impossible without advanced analytical techniques, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). In its granular form, it is visually indistinguishable from many other minerals. ## Distinguishing from Similar Minerals It can be confused with other minerals from the eudialyte group, such as eudialyte itself, kentbrooksite, or oneillite. Differentiation requires precise determination of chemical composition, especially the content of sodium, manganese, iron, zirconium, and niobium. ## Crystal Forms Siudaite occurs exclusively as anhedral, irregular grains intergrown in the rock. No well-formed crystals have been observed.

Geological environment

## Genesis Siudaite formed under hydrothermal conditions, crystallizing in veins cutting nepheline syenites. It is a product of late stages of crystallization of alkaline magma, rich in rare elements. ## Mineral Associations This mineral co-occurs with other minerals from the eudialyte group, as well as with microcline, nepheline, aegirine, sodalite, lorenzenite, and eudialyte. ## Localities The only confirmed occurrence of siudaite in the world is its type locality: San Gabriel mine, Poudrette volcano, Antofagasta region in northern Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a siudaite specimen depends solely on the abundance and size of the mineral grains within the rock matrix and the presence of well-identified associated minerals. Since it does not form aesthetic crystals, its value is purely scientific and systematic. ## Popular Localities The only source of material is the San Gabriel mine in Chile, which makes every specimen from this locality unique.

Care and storage

## Cleaning Specimens containing siudaite, due to their microscopic nature and the brittleness of the grains, should not be cleaned mechanically or chemically. Any attempts at cleaning may lead to damage or loss of material. ## What to Avoid Contact with chemicals, ultrasonic cleaning, and sudden temperature changes should be avoided. The mineral is sensitive to acids. ## Storage Samples containing siudaite should be stored under stable conditions, in sealed "micromount" containers, protecting them from dust, moisture, and mechanical damage.

Sources

IMA Mineral List (CNMNC)