Hingganite-(Nd)

Chemical formula: Nd₂&#₉₇₂₃;Be₂Si₂O₈(OH)₂

Hingganite-(Nd) is a very rare mineral from the gadolinite group, a neodymium beryllium silicate, forming small, prismatic crystals.

## Characteristics Hingganite-(Nd) is a mineral belonging to the gadolinite group, specifically to the datolite subgroup. It occurs as very small, elongated, prismatic crystals, which can form radial or spherulitic aggregates. The crystals are usually transparent to translucent and exhibit a vitreous luster. Due to the small size of the crystals, its features are often studied under a microscope. ## Physical Properties This mineral has a Mohs hardness of approximately 6. It is relatively dense, with a calculated density of 4.86 g/cm³. The crystals show weak cleavage. The luster is described as vitreous. ## Colors and Varieties The observed colors of hingganite-(Nd) range from pale green to yellowish-green. No commercial or colored varieties are known. ## History and Name The mineral's name refers to its chemical composition, indicating the dominance of neodymium (Nd) in a specific position within the crystal structure, and its relation to other minerals of the hingganite series. It was formally described and approved by the International Mineralogical Association (IMA) under number 2009-080. The first scientific description was provided by G. Giester et al. in 2011. ## Applications Hingganite-(Nd) has no industrial applications. Its significance is purely scientific and as a collector's item, being a very rare representative of rare earth minerals.

Properties

Mohs hardness: 5.5-6
Color: Dark greenish-brown
Luster: Vitreous
Streak: White
Density: 4.690
Cleavage: Poor on {001}
Fracture: Conchoidal
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of hingganite-(Nd) is possible almost exclusively through advanced analytical methods, such as energy-dispersive spectroscopy (EDS) or electron microprobe analysis (EMPA), which confirm its unique chemical composition with neodymium dominance. Visually, it is practically indistinguishable from other minerals of the hingganite group without chemical analysis. ## Distinguishing from Similar Minerals It can be confused with other minerals from the gadolinite group, especially hingganite-(Y), hingganite-(Ce), and gadolinite. They differ in the dominant rare earth element in their structure, which is impossible to determine without specialized equipment. It may also resemble some tourmalines or epidote, but differs from them in hardness and, most importantly, in its environment of occurrence. ## Crystal Forms It forms elongated, prismatic crystals, often terminated by a pyramid. These crystals group into radial or stellate aggregates.

Geological environment

## Genesis Hingganite-(Nd) forms in the late stages of crystallization in granitic pegmatites, especially those enriched in rare earth elements and beryllium. It is a secondary mineral, forming as a result of hydrothermal and metasomatic processes that modify pre-existing minerals. ## Mineral Associations It co-occurs with minerals such as quartz, microcline, albite, fluorite, allanite-(Ce), bastnäsite-(Ce), and other rare earth minerals. ## Localities The only confirmed locality (type locality) for this mineral is the Rappold granite quarry in Gföhl, in the Waldviertel region of Lower Austria.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromorphological mineral, the most important quality criterion is excellent crystal habit and transparency, even if they are very small. Specimens where crystals form aesthetic, radial aggregates on a well-chosen rock matrix are most desirable. The size of individual crystals rarely exceeds 1-2 mm, so any larger specimen is exceptional. ## Popular Localities The only source of specimens is the type locality – the Rappold quarry in Austria. Material from this location is extremely rare and sought after by specialized collectors of systematic minerals and micromounts.

Care and storage

## Cleaning Due to its extreme rarity and small specimen sizes, mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Avoid ultrasonic cleaners, chemical agents, acids, and sudden temperature changes. The mineral is brittle and susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized mineral boxes (e.g., "membrane boxes" or small boxes with soft padding) to protect them from damage and dust. Avoid exposure to shocks and vibrations.

External references

https://www.mindat.org/min-47711.html