Rowlandite-(Y)

Chemical formula: Fe₂+Y₄(Si₂O₇)₂F₂

Rowlandite-(Y) is a rare yttrium iron silicate, forming massive aggregates with a vitreous luster and a greenish or brownish coloration.

## Characteristics Rowlandite-(Y) is a mineral belonging to the silicate group, chemically classified as a yttrium iron silicate with fluorine. It is rare, most often occurring as irregular, massive aggregates or grains embedded in the host rock. Well-formed crystals are extremely rare. It is usually opaque, and its surfaces exhibit a luster ranging from vitreous to greasy or resinous. ## Physical Properties This mineral is characterized by a hardness of 5.5-6.5 on the Mohs scale, making it relatively resistant to scratching. Its density is quite high, approximately 4.55 g/cm³. It shows no cleavage, and its fracture is conchoidal to uneven. It is brittle. ## Colors and Varieties Rowlandite-(Y) most often exhibits colors ranging from pale green, olive green to brownish and almost black. The coloration is often non-uniform. No named varieties are distinguished. ## History and Name The mineral was first described in 1891 by William Hillebrand, who found it in a pegmatite at Baringer Hill in Texas, USA. The name "rowlandite" was given in honor of Henry Augustus Rowland (1848-1901), an American physicist from Johns Hopkins University. The suffix "-(Y)" was added later, in accordance with rare-earth mineral naming conventions, to indicate yttrium (Y) as the dominant element in a specific crystallographic site. ## Uses Rowlandite-(Y) has no industrial applications. Its significance is limited to the scientific and collecting spheres, as a rare yttrium-bearing mineral.

Properties

Mohs hardness: 5.5-6.5
Luster: Vitreous to resinous
Streak: Greenish-gray
Density: 4.55
Cleavage: None
Fracture: Conchoidal to uneven
Transparency: Translucent to opaque
Crystal system: Triclinic

Diagnostic features

## Identification Rowlandite-(Y) in its typical massive form is recognized by its greenish or brownish color, vitreous to greasy luster, high density, and lack of cleavage. Its conchoidal fracture is also characteristic. Its occurrence in granite pegmatites rich in rare-earth elements is a key indicator. ## Distinguishing from Similar Minerals This mineral can be confused with other massive rare-earth silicates, such as gadolinite-(Y) or allanite. Gadolinite-(Y) is usually black and has similar hardness and fracture, but often forms better-developed crystals. Allanite can also be black or brownish, but it crystallizes in the monoclinic system. Accurate differentiation of these minerals often requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis. ## Crystal Forms Well-formed crystals are exceptionally rare. This mineral most often forms irregular, massive aggregates, grains, or nodules embedded in the rock.

Geological environment

## Genesis Rowlandite-(Y) is a magmatic mineral, crystallizing in the late stages from residual melts in granite pegmatites that are enriched in rare-earth elements, especially yttrium. ## Mineral Associations This mineral co-occurs with other minerals typical of rare-earth pegmatites. The most common associations include quartz, microcline, albite, biotite, gadolinite-(Y), allanite, fergusonite, cyrtolite (a variety of zircon), and fluorite. ## Localities The most important and historical locality is Baringer Hill in Llano County, Texas, USA, from where the first described specimens originated. Other known localities include pegmatites in the Iveland area in Norway, and some sites in Sweden and Japan.

Rarity

Very rare

For collectors

## Quality Criteria The collector quality of rowlandite-(Y) is difficult to assess due to its rarity and typically massive form. The most prized specimens are those that exhibit a distinct, attractive color (e.g., intense green) and luster. Large, rich fragments of the mineral in the host rock (matrix) are more desirable than small, isolated grains. Any specimen with visible, even imperfect, crystal faces is considered exceptional. ## Popular Localities Classic and most well-known specimens come from the historical locality of Baringer Hill in Texas, USA. This site is currently flooded, making material from there very rare and historically valuable. Specimens from Norwegian pegmatites also appear on the collector's market.

Care and storage

## Cleaning Rowlandite-(Y) specimens can be cleaned with a soft, dry brush to remove dust. If necessary, distilled water may be used, but prolonged soaking should be avoided. After wet cleaning, the specimen should be thoroughly dried. ## What to Avoid Avoid contact with strong acids and other aggressive chemicals. The mineral is brittle, so it must be protected from impacts and falls. Some specimens may be sensitive to rapid temperature changes. ## Storage It is recommended to store specimens in individual, padded boxes or on stable stands to prevent scratches and mechanical damage. Display should protect the mineral from dust and direct sunlight, which could theoretically affect its color.

Sources

IMA Mineral List (CNMNC)