Bussyite-(Y)
Chemical formula: (Y,REE,Ca)₃(Na,Ca)₆Mn²⁺Si₉Be₅(O,F,OH)₃₄
Bussyite-(Y) is a rare silicate mineral, found as platy, dark brown crystals, discovered in the famous Poudrette quarry in Canada.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- White
- Density
- 3.11
- Cleavage
- {101}
- Fracture
- Splintery
- Transparency
- Transparent,Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Bussyite-(Y) can be recognized by its characteristic form – thin, platy crystals forming fan-shaped or rosette-like aggregates. Its dark brown color, vitreous luster, and occurrence in a specific geological environment (nepheline syenite pegmatites) are key features. It is relatively soft (hardness 4). ## Distinguishing from Similar Minerals It can be confused with other rare, brown minerals from Mont Saint-Hilaire, such as some micas or astrophyllite. It differs from astrophyllite by the absence of a brownish-golden hue and a different crystal habit. It differs from micas by the lower flexibility of its lamellae and its specific, fan-shaped aggregate arrangement. Certain identification requires advanced analytical methods (e.g., EDS). ## Crystal Forms Crystals are thin, platy, with a hexagonal or rectangular outline. They most often occur as fan-shaped, spherulitic, or rosette-like aggregates, where individual crystals radiate from a common center.
Geological environment
## Genesis Bussyite-(Y) is an igneous mineral, crystallizing in the late stages of the evolution of pegmatites associated with alkaline nepheline syenite intrusions. It forms under conditions of high concentration of rare earth elements (especially yttrium), beryllium, sodium, and manganese. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Mont Saint-Hilaire environment. Its paragenesis includes, among others, analcime, aegirine, microcline, nepheline, sodalite, catapleiite, eudialyte, sérandite, and polylithionite. ## Localities The only confirmed and described locality for bussyite-(Y) in the world is its type locality – the Poudrette quarry (Mont Saint-Hilaire) in Quebec, Canada. This is one of the most famous mineralogical sites in the world, known for the occurrence of hundreds of rare and unique minerals.
Rarity
Very rare
For collectors
## Quality Criteria The most prized specimens of bussyite-(Y) are those that exhibit well-formed, sharp, and undamaged fan-shaped or rosette-like crystal aggregates. A clear contrast with the rock matrix on which they occur is important. The size of the aggregates is a key factor – specimens exceeding several millimeters are already considered significant. The purity of the specimen and the absence of mechanical damage increase its value. ## Popular Localities The only source of bussyite-(Y) specimens is the Poudrette quarry in Mont Saint-Hilaire, Canada. All specimens available on the collector's market originate from this single locality, which makes them particularly sought after by specialists collecting systematic minerals or minerals from this specific locality.
Care and storage
## Cleaning Bussyite-(Y) specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its softness and potential reactivity, avoid washing in water, and especially avoid using ultrasonic cleaners, which could damage delicate crystals. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is relatively soft, so it must be protected from scratching by harder minerals (e.g., quartz). It should not be heated or exposed to sudden temperature changes. ## Storage Collectible specimens of bussyite-(Y) are best stored in separate, sealed display boxes, lined with soft material, to prevent mechanical damage and dust accumulation. Protect from direct sunlight, although its light sensitivity is not known.