Barrydawsonite-(Y)

Chemical formula: Na<sub>1.5</sub>Y<sub>0.5</sub>CaSi<sub>3</sub>O<sub>9</sub>H

A rare sodium, calcium, and yttrium silicate, forming colorless, lath-like crystals in geologically unique locations.

## Characteristics Barrydawsonite-(Y) is a very rare mineral from the silicate group, chemically classified as a complex sodium, calcium, and yttrium silicate. It occurs as small, colorless, lath-like or acicular crystals, rarely exceeding 1 mm in length. These crystals form radiating or haphazardly arranged aggregates in rock fissures. Due to their size and transparency, individual crystals are difficult to observe with the naked eye and usually require magnification. ## Physical Properties The mineral is characterized by a vitreous luster. It is transparent to translucent. Its Mohs hardness is approximately 4, and its density is slightly higher than average for silicates, at about 2.92 g/cm³. ## History and Name Barrydawsonite-(Y) was first described in 2005 by G. Giester, C. L. Lengauer, E. Tillmanns, and J. Zuska. Its name honors John Barry Dawson (1932–2013), a British geologist and professor at the University of Edinburgh, for his significant contributions to the petrology of alkaline rocks and kimberlites. The suffix "-(Y)" in the name refers to the dominant rare-earth element in its composition, which is yttrium (Y).

Properties

Mohs hardness
4
Luster
Vitreous
Streak
White
Density
2.92
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Amateur identification of barrydawsonite-(Y) is practically impossible. It requires advanced analytical techniques such as X-ray diffraction (XRD) and chemical composition analysis (EDS/WDS), due to its occurrence as microscopic crystals and its resemblance to other silicates. ## Distinguishing from Similar Minerals It can be confused with many other rare silicates found in similar parageneses, such as eudialyte, catapleiite, or sérandite, but it differs from them in crystal habit and chemical composition. Definitive differentiation requires specialized studies. ## Crystal Forms It forms elongated, lath-like or acicular crystals, often flattened. These crystals group into radiating or chaotic aggregates.

Geological environment

## Genesis Barrydawsonite-(Y) is a hydrothermal mineral, crystallizing in the late stage of evolution of highly differentiated, alkaline igneous intrusions, such as nepheline syenites. It forms in rock cavities and fissures as a result of solutions rich in sodium, calcium, and rare-earth elements. ## Mineral Associations This mineral coexists with other rare minerals typical of alkaline environments. In its type locality (Mont Saint-Hilaire), it was found in association with analcime, eudialyte, catapleiite, sérandite, aegirine, and microcline. ## Localities The only confirmed and detailed described occurrence of barrydawsonite-(Y) in the world is the Poudrette quarry at Mont Saint-Hilaire, in the Montérégie region of Quebec, Canada. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the value of a specimen is primarily determined by the abundance and quality of crystals visible under magnification. The most desirable specimens are those with well-formed, sharp, and undamaged crystals, forming aesthetic, radiating aggregates. Contrast with the rock matrix and the presence of interesting associated minerals are also important. ## Popular Localities The only source of specimens is the Poudrette quarry at Mont Saint-Hilaire in Canada, which is known for yielding hundreds of unique and rare mineral species.

Care and storage

## Cleaning Specimens should be cleaned with extreme caution, using only a soft brush to remove dust. Due to the mineral's rarity and delicacy, the use of water or any chemical agents is discouraged. ## What to Avoid Avoid contact with chemicals, acids, and detergents. The mineral is relatively soft, so it must be protected from scratches and impacts. Ultrasonic cleaning should not be used. ## Storage It is recommended to store specimens in stable conditions, in sealed "micromount" boxes, which protect them from mechanical damage, dust, and sudden changes in humidity.

Sources

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