Reederite-(Y)

Chemical formula: (Na,Mn²⁺)₁₅Y₂(CO₃)₉(S⁶⁺O₃F)Cl

Reederite-(Y) is a rare, transparent mineral with a yellow to orange-brown color, discovered in the famous Poudrette quarry in Canada.

## Characteristics Reederite-(Y) is a complex carbonate of sodium, manganese, and yttrium, also containing fluorine, sulfur, and chlorine. It forms small, tabular or hexagonal crystals, rarely exceeding a few millimeters in size. It typically occurs as single, well-formed crystals or small aggregates. It is a transparent mineral, valued for its intense, yellow to orange-brown color and vitreous luster. ## Physical Properties This mineral is characterized by a relatively low hardness, ranging from 3 to 3.5 on the Mohs scale, which makes it quite brittle. Its density is approximately 2.91 g/cm³. It exhibits distinct cleavage in one direction and a conchoidal fracture. The luster is typically vitreous. ## Colors and Varieties Reederite-(Y) occurs in shades from light yellow, through golden yellow, to orange-brown. No distinct color varieties or commercial forms have been identified. ## History and Name The mineral's name honors George E. Reeder, an American analytical chemist with the U.S. Geological Survey, for his contributions to the chemical analysis of minerals. The "-(Y)" suffix in the name indicates the dominance of yttrium in its chemical composition. It was first described in 1995 based on specimens found in the Poudrette quarry at Mont Saint-Hilaire, Canada. ## Applications Due to its extreme rarity and small crystal size, Reederite-(Y) has no industrial applications. It is of purely scientific and collector interest, being a sought-after micromineral among advanced collectors.

Properties

Mohs hardness: 3-3.5
Luster: Vitreous
Streak: White
Density: 2.91
Cleavage: {001}
Fracture: Conchoidal
Transparency: Transparent
Crystal system: Hexagonal

Diagnostic features

## Identification Key diagnostic features include its hexagonal crystal habit, characteristic yellow to orange-brown color, vitreous luster, and low hardness. Its occurrence in the specific geological environment of Mont Saint-Hilaire is also a strong indicator. ## Distinguishing from Similar Minerals It can be confused with other yellow minerals from Mont Saint-Hilaire, such as sirsanite or some microlites. However, definitive differentiation requires advanced analytical methods, such as spectroscopy or chemical analysis, due to visual similarities and co-occurrence. ## Crystal Forms It forms thin, tabular crystals with a hexagonal outline. They occur as single, isolated crystals or in small, loose groups.

Geological environment

## Genesis Reederite-(Y) forms in the late stages of hydrothermal processes within highly differentiated, alkaline nepheline syenite intrusions. It crystallizes in rock cavities and fractures, often within sodalite xenoliths or marbles. ## Mineral Associations This mineral co-occurs with a wide range of other rare minerals typical of the Mont Saint-Hilaire locality. The most important include eudialyte, sodalite, aegirine, microcline, nepheline, catapleiite, sirsanite, and petersenite-(Ce). ## Localities The only confirmed and described occurrence of Reederite-(Y) in the world is its type locality – the Poudrette quarry (Mont Saint-Hilaire) in the Montérégie region, Quebec, Canada.

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens are those with sharply defined, well-formed crystals of intense, golden yellow or orange color. Transparency and lack of damage are important. A contrasting placement on a rock matrix, for example with white sodalite or dark aegirine, significantly enhances the aesthetic and collector value of the specimen. ## Popular Localities All known and valued Reederite-(Y) specimens come from a single location in the world: the Poudrette quarry at Mont Saint-Hilaire, Canada. This is one of the most famous mineralogical localities, known for the occurrence of hundreds of unique and rare minerals.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to potential reactivity, the use of water or any chemical agents is not recommended. Dry cleaning is the safest method. ## What to Avoid Contact with water, acids, and other chemicals should be strictly avoided. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. It should not be heated or subjected to ultrasound. ## Storage Reederite-(Y) should be stored in stable conditions, away from moisture and chemical contaminants. The best solution is to place it in a sealed "micromount" box, which protects the delicate specimen from mechanical damage and dust.