Carbokentbrooksite
Chemical formula: (Na,☐)<sub>12</sub>(Na,Ce<sup>3+</sup>)<sub>3</sub>Ca<sub>6</sub>Mn<sup>2+</sup><sub>3</sub>Zr<sup>4+</sup><sub>3</sub>Nb<sup>5+</sup>Si<sub>25</sub>O<sub>73</sub>(OH)<sub>3</sub>(CO<sub>3</sub>)·H<sub>2</sub>O
Carbokentbrooksite is an extremely rare mineral of the eudialyte group, characterized by a complex chemical composition and occurring as fine grains in alkaline massifs.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.05
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of carbokentbrooksite is only possible using advanced analytical methods, such as X-ray microanalysis (EDS/WDS) and X-ray diffraction (XRD), due to its microscopic size and co-occurrence with many similar minerals of the eudialyte group. Visual characteristics, such as its pale yellow color and occurrence in a characteristic geological environment, can only serve as an initial indication. ## Distinguishing from Similar Minerals It can be confused with other minerals of the eudialyte group, such as kentbrooksite, eudialyte, or oneillite, which often co-occur in the same rocks. Differentiation requires precise chemical analysis to determine the presence and proportion of key elements, especially the carbonate group, manganese, niobium, and zirconium. ## Crystal Forms This mineral forms only small, irregularly shaped (anhedral) grains within other rock-forming minerals.
Geological environment
## Genesis Carbokentbrooksite forms in the late stages of crystallization of highly differentiated alkaline magmas. It occurs in pegmatites and hydrothermal veins cutting nepheline syenites and related rocks. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline pegmatites, such as eudialyte, microcline, nepheline, aegirine, albite, natrolite, lorenzenite, as well as other rare minerals of the eudialyte group. ## Localities The only confirmed and thoroughly described occurrence (type locality) is the Ilímaussaq alkaline complex in southern Greenland. This is a classic and one of the most important worldwide localities for alkaline rock minerals.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a carbokentbrooksite specimen depends on the size and quality of the grains, as well as the richness of its association with other rare minerals. The most valued specimens are those where carbokentbrooksite grains, despite their small size, are clearly visible and well-defined against the host rock. Due to the microscopic nature of the mineral, precise documentation and analytical confirmation of its identity are crucial. ## Popular Localities The only source of collectible specimens is the Ilímaussaq complex in Greenland. Material from this locality is highly prized by collectors specializing in rare minerals and so-called "micromounts."
Care and storage
## Cleaning Specimens containing carbokentbrooksite, typically microscopic grains within the host rock, do not require and should not undergo mechanical or chemical cleaning. Any attempts at cleaning may damage or dislodge the delicate mineral grains. Only gentle blowing with compressed air to remove dust is permissible. ## What to Avoid Avoid contact with any chemicals, especially acids, which can react with the mineral's components. Also, avoid ultrasonics, high temperatures, and sudden temperature changes. ## Storage "Micromount" specimens should be stored in specialized, sealed boxes (so-called "micromount boxes") that protect them from dust, moisture, and mechanical damage. Store under stable room conditions, away from direct sunlight.