Pseudodickthomssenite

Chemical formula: Mg(V₅+O₃)₂·₈H₂O

Pseudodickthomssenite is a very rare, hydrated magnesium vanadate, forming microscopic, colorless, bladed crystals.

## Characteristics Pseudodickthomssenite is a hydrated magnesium vanadate, occurring as extremely small, colorless, and transparent crystals. It typically forms aggregates composed of very fine, bladed or acicular crystals, which can reach up to 0.2 mm in length. Due to its microscopic size, its visual characteristics are difficult to assess without specialized equipment. ## Physical Properties Pseudodickthomssenite crystals are characterized by a vitreous luster. They are transparent and colorless. Hardness and density have not been precisely determined due to the small size and rarity of the material. ## Colors and Varieties This mineral is naturally colorless. No colored varieties are known. ## History and Name Pseudodickthomssenite was first described in 2023 by Anthony R. Kampf and his team. The name refers to its structural and chemical similarity to dickthomssenite, with the prefix "pseudo" referring to the different crystal symmetry (monoclinic in pseudodickthomssenite, orthorhombic in dickthomssenite). It was approved by the International Mineralogical Association (IMA) under number IMA2023-014. The type locality is the St. Jude mine in San Miguel County, Colorado, USA.

Properties

Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of pseudodickthomssenite is only possible using advanced laboratory methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS). Visual identification in the field or even in a collection is impossible due to its microscopic size and lack of characteristic macroscopic features. ## Distinguishing from Similar Minerals It can be confused with dickthomssenite, to which it is closely related. Differentiation requires crystallographic analysis, as pseudodickthomssenite crystallizes in the monoclinic system, and dickthomssenite in the orthorhombic system. Other colorless, secondary vanadium minerals may also appear similar under the microscope. ## Crystal Forms Crystals are in the form of very thin, elongated blades or needles, often gathered in small, radial or chaotic aggregates.

Geological environment

## Genesis Pseudodickthomssenite is a secondary mineral, forming in the oxidation zones of uranium-vanadium deposits in sedimentary rocks, mainly sandstones. It forms as a result of the weathering processes of primary vanadium minerals under conditions of low temperature and pressure. ## Mineral Associations At the type locality (St. Jude mine, Colorado), it co-occurs with quartz, gypsum, dickthomssenite, sherwoodite, and other secondary vanadium minerals. ## Localities The only confirmed occurrence of pseudodickthomssenite in the world is its type locality - the St. Jude mine in the Slick Rock district, San Miguel County, Colorado, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, the collectible value of a specimen depends on the presence of well-formed, albeit microscopic, crystals that are clearly visible against the matrix rock. The most valuable specimens are rich crystal aggregates or specimens where pseudodickthomssenite co-occurs with other rare secondary minerals. ## Popular Localities The only source of specimens is the St. Jude mine in Colorado, USA. Material from this locality is highly sought after by collectors specializing in rare and "micromount" minerals.

Care and storage

## Cleaning Due to the extreme rarity and microscopic size of the crystals, mechanical cleaning is neither recommended nor possible. Specimens should be protected from dust and contamination. ## What to Avoid Contact with any chemicals, including water, which can dissolve or damage the delicate crystals, should be avoided. Temperature changes, vibrations, and shocks should also be avoided. ## Storage Pseudodickthomssenite specimens, usually as particles on matrix rock, should be stored exclusively in specialized, sealed "micromount" boxes. This protects them from dust, moisture, and mechanical damage.

Sources

IMA Mineral List (CNMNC)