Horváthite-(Y)

Chemical formula: NaY(CO<sub>₃</sub>)F<sub>₂</sub>

A rare yttrium carbonate-fluoride, forming characteristic aggregates of tabular crystals, known primarily from Mont Saint-Hilaire, Canada.

## Characteristics Horváthite-(Y) is a rare mineral from the carbonate group, chemically classified as a hydrated sodium yttrium carbonate-fluoride. It forms very small, yet well-formed crystals with a tabular or platy habit. Most often, they occur as complex aggregates – rosettes, spherulites, or hemispherical clusters, reaching several millimeters in diameter. Visually, specimens are subtle, and their structure is best observed under magnification. ## Physical Properties This mineral has a hardness of 4 on the Mohs scale, making it relatively soft. It has a vitreous luster and is transparent to translucent. Its density is approximately 3.58 g/cm³, which is a relatively high value for a mineral with a non-metallic composition. ## Colors and Varieties Horváthite-(Y) is most often colorless or white. Specimens with very delicate hues, such as pale pink or pale yellow, are also found. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral's name honors László and Elsa Horváth, Canadian mineral collectors who made significant contributions to the understanding of the mineralogy of the Mont Saint-Hilaire deposit. The suffix "-(Y)" indicates the dominance of yttrium in its chemical composition. The mineral was officially recognized by the International Mineralogical Association (IMA) in 1997. The type locality is the Poudrette quarry in Mont Saint-Hilaire, Quebec, Canada. ## Applications Due to its rarity and small crystal size, horváthite-(Y) has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced collections of rare and systematic minerals.

Properties

Mohs hardness: 4
Color: Colorless to pale beige
Luster: Vitreous
Streak: White
Density: 3.58
Cleavage: {100} very good, {010} good
Fracture: Irregular/Uneven
Transparency: Transparent,Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification The most characteristic feature of horváthite-(Y) is its mode of occurrence – aggregates of small, tabular crystals forming rosettes and spherulites. In combination with its vitreous luster, relatively high density, and specific environment of occurrence (alkaline pegmatites), this allows for preliminary identification. ## Distinguishing from Similar Minerals At first glance, it may be confused with other white or colorless tabular minerals from Mont Saint-Hilaire, such as catapleiite or gaidonnayite. It differs from catapleiite in its crystallographic system (orthorhombic, not hexagonal) and the absence of catapleiite's characteristic pseudohexagonal form. Definitive distinction from similar rare minerals requires advanced analytical methods, such as EDS spectroscopy or X-ray diffraction (XRD). ## Crystal Forms Crystals are tabular, flattened along one of the crystallographic axes. They almost never occur as single, isolated individuals. They usually form radial or spherical aggregates, in which individual crystals are arranged like flower petals.

Geological environment

## Genesis Horváthite-(Y) is a hydrothermal mineral, crystallizing in the late stages of the evolution of nepheline syenite pegmatites. It forms in vugs and fractures (miarolitic cavities) within these alkaline intrusions, at relatively low temperatures. ## Mineral Associations It most often co-occurs with other minerals typical of the alkaline environment of Mont Saint-Hilaire. Its typical associations include: aegirine, albite, analcime, catapleiite, eudialyte, gaidonnayite, griceite, lorenzenite, microcline, natrolite, nepheline, rhodochrosite, sérandite, and sodalite. ## Localities This is a very rare mineral, known from only a few localities worldwide. The most important and type locality, from which the best specimens originate, is the Poudrette quarry, Mont Saint-Hilaire in Quebec, Canada. Its occurrence has also been confirmed in the Darai-Pioz massif in Tajikistan and on the Kola Peninsula in Russia.

Rarity

Extremely Rare

For collectors

## Quality Criteria The most highly valued specimens are those with well-formed, sharp, and distinct crystal rosettes. The size of the aggregates is important – the larger, the more valuable. Transparency and lack of damage are also desirable. Specimens where horváthite-(Y) contrasts with the matrix or co-occurs in an aesthetic composition with other rare minerals from the given locality are particularly attractive. ## Popular Localities The vast majority, if not all, specimens available on the collector's market come from a single location – the Poudrette quarry in Mont Saint-Hilaire, Canada. This is the classic locality for this mineral, and specimens from there serve as the standard for the species.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush and distilled water. Avoid strong water jets, which could damage delicate aggregates. Ultrasonic cleaners are not recommended. ## What to Avoid The mineral is sensitive to acids, which cause its decomposition. As it is relatively soft (hardness 4), it is susceptible to scratches from harder minerals and tools. It should be protected from impacts and falls, which can cause damage along cleavage planes. ## Storage It is recommended to store specimens in separate, sealed membrane boxes or in display cases with soft lining. This protects delicate crystals from dust, mechanical damage, and contact with other minerals.

Sources

IMA Mineral List (CNMNC)