Ferrokentbrooksite

Chemical formula: Na₁₅Ca₆Fe²⁺₃Zr⁴⁺₃Nb⁵⁺(Si₂₅O₇₃)(O,OH,H₂O)₃(F,Cl)₂

Ferrokentbrooksite is a rare mineral from the eudialyte group, distinguished by its reddish-brown color and complex chemical composition containing iron, zirconium, and niobium.

## Characteristics Ferrokentbrooksite is a complex cyclosilicate belonging to the eudialyte group. It forms small, well-formed crystals, typically tabular or rhombohedral in habit. Its characteristic feature is an intense, reddish or reddish-brown color. Specimens are usually transparent and exhibit a vitreous luster, making them attractive for micromount collecting. ## Physical Properties This mineral is characterized by a hardness of 5-6 on the Mohs scale. Its density is approximately 3.06 g/cm³. It does not exhibit cleavage, and its fracture is uneven, sometimes conchoidal. The luster is typically vitreous. ## Colors and Varieties Ferrokentbrooksite occurs in shades from red to reddish-brown. No distinct color varieties or commercial names have been identified. ## History and Name The name "ferrokentbrooksite" refers to its chemical composition – the dominance of iron (ferro) – and its relation to the associated mineral kentbrooksite. It was described as a new mineral in 2001 by G. Grice and G. Gault based on material from the Poudrette quarry at Mont Saint-Hilaire, Canada. ## Applications Due to its rarity and small crystal size, ferrokentbrooksite has no industrial applications. It is solely an object of interest for collectors and a subject of scientific research.

Properties

Mohs hardness: 5-6
Luster: Vitreous
Streak: white
Density: 3.06
Cleavage: without cleavage
Fracture: Irregular/Uneven,Conchoidal
Transparency: Transparent
Crystal system: Trigonal

Diagnostic features

## Identification Ferrokentbrooksite can be recognized by its characteristic reddish-brown color, vitreous luster, and crystal form. However, its association with the location is key – it occurs in a specific geological environment, namely nepheline syenites at Mont Saint-Hilaire. A white streak and lack of cleavage are additional auxiliary features. ## Distinguishing from Similar Minerals It can be confused with other minerals from the eudialyte group, such as eudialyte itself or kentbrooksite. Definitive and certain differentiation from these minerals requires advanced chemical analyses (e.g., EDS) to determine the exact composition, particularly the content of iron, manganese, and niobium. ## Crystal Forms It most commonly forms small, tabular crystals with a hexagonal outline or rhombohedral crystals. It occurs as single, well-formed crystals embedded in the host rock.

Geological environment

## Genesis Ferrokentbrooksite is a mineral of magmatic origin. It forms in the late stages of crystallization within nepheline syenites and associated pegmatites, in an environment rich in rare earth elements, zirconium, niobium, and fluorine. ## Mineral Associations It co-occurs with other minerals typical of the Mont Saint-Hilaire nepheline syenites, such as microcline, nepheline, aegirine, sodalite, catapleiite, sérandite, and other minerals from the eudialyte group. ## Localities The only confirmed and described occurrence (type locality) of ferrokentbrooksite in the world is the Poudrette quarry in the Mont Saint-Hilaire alkaline complex, Quebec province, Canada. This is one of the most famous mineralogical localities in the world.

Rarity

Very rare

For collectors

## Quality Criteria The most prized ferrokentbrooksite specimens are those with sharply defined, well-formed, and undamaged crystals of intense red color. Specimens where crystals are exposed on a light rock matrix (e.g., on white nepheline or microcline), creating an attractive contrast, are also highly valued. Crystal size is also important, although they rarely exceed a few millimeters. ## Popular Localities The only source of ferrokentbrooksite specimens is its type locality – the Poudrette quarry at Mont Saint-Hilaire, Canada. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Always thoroughly dry the specimen after cleaning. ## What to Avoid Avoid contact with acids and other aggressive chemicals that can damage the mineral's surface. It should not be heated or subjected to sudden temperature changes. As a mineral of moderate hardness, it is susceptible to scratching by harder minerals (e.g., quartz). ## Storage It is recommended to store ferrokentbrooksite specimens in separate, padded display boxes to prevent scratches and mechanical damage. Protect from dust and direct, prolonged exposure to sunlight.