Rogermitchellite
Chemical formula: Na<sub>6</sub>Sr<sub>12</sub>Ba<sub>2</sub>Zr<sup>4+</sup><sub>13</sub>Si<sub>39</sub>B<sub>6</sub>O<sub>123</sub>(OH)<sub>14</sub>·10H<sub>2</sub>O
Rogermitchellite is an extremely rare mineral from the silicate group, distinguished by its exceptionally complex chemical composition and occurrence as colorless or pale yellow crystals.
Description
## Characteristics Rogermitchellite is a mineral with one of the most complex chemical formulas, containing sodium, strontium, barium, zirconium, silicon, and boron. It forms small, prismatic crystals that rarely exceed 0.5 mm in length. They usually occur as small aggregates. It is a transparent mineral with a vitreous luster. ## Physical Properties The Mohs hardness of rogermitchellite is 5. Its density is approximately 3.43 g/cm³. This mineral does not exhibit cleavage, and its fracture is conchoidal. ## Colors and Varieties Crystals are most often colorless, less frequently taking on a pale yellow hue. No color or commercial varieties have been identified. ## History and Name The mineral was officially described in 2021. Its name honors Roger H. Mitchell (born 1941), a retired professor of geology at Lakehead University in Canada, for his contributions to the study of the petrology and mineralogy of alkaline rocks and kimberlites. ## Applications Due to its extreme rarity and microscopic crystal size, rogermitchellite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized mineral collectors (so-called microminerals).
Diagnostic features
## Identification Identifying rogermitchellite based on visual characteristics is practically impossible. Key indicators are: its unique locality (Mont Saint-Hilaire), paragenesis with other rare alkaline minerals, and the characteristic prismatic crystal form. Definitive identification requires advanced analytical techniques, such as X-ray diffraction (XRD) or electron probe microanalysis (EDS/WDS), which can confirm its unique chemical composition. ## Distinguishing from Similar Minerals In its environment of occurrence, it can be confused with many other colorless minerals, such as quartz, analcime, natrolite, or catapleiite. Differentiation requires specialized equipment. It is distinguished from similar minerals by its trigonal crystal system and the simultaneous presence of strontium, barium, zirconium, and boron in its structure. ## Crystal Forms It forms hexagonal, prismatic crystals up to 0.5 mm long, terminated by a pyramid. Crystals often occur in tangled or radial aggregates.
Geological environment
## Genesis Rogermitchellite forms under specific geochemical conditions. It was found in a xenolith (a fragment of foreign rock) embedded within a nepheline syenite dike. This environment is strongly alkaline and silica-undersaturated, which favors the crystallization of minerals rich in rare elements. ## Mineral Associations This mineral occurs in association with other rare minerals typical of Mont Saint-Hilaire, such as aegirine, albite, analcime, catapleiite, eudialyte, lorenzenite, microcline, nepheline, sodalite, steacyite, and vlasovite. ## Localities The only confirmed locality of rogermitchellite in the world (type locality) is the Poudrette Quarry, located on Mont Saint-Hilaire in Quebec, Canada. This is one of the most famous mineralogical localities worldwide.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For such a rare micromineral, specimens with sharply terminated, well-formed, and transparent crystals are most highly valued. Crystal size is also important – even if they are submillimeter, larger ones are considered more valuable. The attractiveness of a specimen is enhanced by its aesthetic placement on the rock matrix and the presence of other rare, well-formed associated minerals. ## Popular Localities All known rogermitchellite specimens originate from a single location in the world – the Poudrette Quarry in Mont Saint-Hilaire, Canada. This locality is known for providing the best and only specimens of this mineral.
Care and storage
## Cleaning Rogermitchellite specimens are almost exclusively microminerals, which are very delicate. Cleaning should be limited to an absolute minimum. Compressed air can be used from a safe distance to remove dust. Contact with water and any chemical agents should be avoided. ## What to Avoid Ultrasonic cleaners, solvents, acids, and bases should be strictly avoided. The mineral's reaction to temperature changes and prolonged exposure to sunlight is unknown, so it is recommended to store it under stable conditions. ## Storage The safest storage method is to place the specimen in a sealed "micromount" box, which protects it from dust, moisture, and mechanical damage.