Hundholmenite-(Y)

Chemical formula: (Y,REE,Ca,Na)₁₅(Al,Fe₃+)CaxAs₃+₁-x(Si,As₅+)Si₆B₃(O,F)₄₈

Hundholmenite-(Y) is an extremely rare, white to colorless silicate mineral, distinguished by its complex chemical composition with the presence of yttrium and arsenic.

## Characteristics Hundholmenite-(Y) is a very rare silicate mineral with a complex chemical structure, classified as a member of the okanoganite supergroup. It forms small, tabular or platy crystals, usually not exceeding 1 mm in size, which often occur in radial or randomly oriented aggregates. It is a colorless to white mineral with a vitreous luster. ## Physical Properties Hundholmenite-(Y) crystals exhibit a hardness of approximately 5 on the Mohs scale. The mineral is transparent to translucent. Its density is about 4.03 g/cm³. ## History and Name The mineral's name comes from its discovery locality – the Hundholmen pegmatite in Tysfjord, Nordland region, Norway. It was officially recognized by the International Mineralogical Association (IMA) in 2007 under number IMA2007-032. The "(Y)" suffix in the name indicates the dominance of yttrium in its chemical composition.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 4.03
Cleavage: None
Fracture: Uneven
Transparency: Transparent to Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identifying hundholmenite-(Y) based on visual characteristics is practically impossible and requires advanced analytical techniques, such as electron spectroscopy (EDS/WDS) to confirm its unique chemical composition (presence of yttrium, arsenic, boron, and silicon) and X-ray diffraction (XRD) to identify its crystal structure. ## Distinguishing from Similar Minerals It can be confused with other rare silicates found in the same environment, such as kapitsaite-(Y) or okanoganite-(Y), from which differentiation is only possible through chemical and structural analysis. ## Crystal Forms It forms thin, tabular or platy crystals that combine into radial or disordered aggregates. Crystals are usually very small, rarely exceeding 1 mm in length.

Geological environment

## Genesis Hundholmenite-(Y) forms in granitic syenite pegmatites, under conditions enriched in rare earth elements (especially yttrium), boron, and arsenic. ## Mineral Associations It coexists with minerals such as albite, microcline, quartz, zircon, thuringite, stilpnomelane, fluorite, steacyite, kapitsaite-(Y), and okanoganite-(Y). ## Localities The only confirmed occurrence of this mineral in the world is its type locality – the Hundholmen pegmatite in Tysfjord, Nordland region, Norway.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, its collector value primarily depends on the richness and development of crystals within the aggregate, as well as the presence of associated minerals. Specimens with clearly visible, well-formed crystals abundantly covering the rock matrix are most highly prized. Due to its extreme rarity, every authentic specimen is considered very valuable. ## Popular Localities The Hundholmen pegmatite in Norway is the sole source of specimens, making it one of the most sought-after minerals for collectors specializing in systematics and rare species.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove loose dust particles. Avoid contact with water and chemicals. ## What to Avoid Avoid ultrasonic cleaners, steam cleaners, acids, and all chemical solvents. The mineral should be protected from high temperatures and sudden temperature changes. Due to the small size of the crystals, it is very susceptible to mechanical damage. ## Storage Hundholmenite-(Y) specimens should be stored exclusively in specialized "micromount" boxes, protecting them from dust, moisture, and physical damage. Avoid exposure to direct sunlight, although there is no evidence of fading.

Sources

IMA Mineral List (CNMNC)