Devilliersite
Chemical formula: Ca₄Ca₂Fe³⁺₁₀O₄[(Fe³⁺₁₀Si₂)O₃₆]
Devilliersite is a very rare iron and calcium silicate, discovered in Israel, belonging to the sapphirine supergroup.
Properties
- Luster
- Metallic
- Streak
- Black
- Transparency
- Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Identification of devilliersite is possible only through advanced laboratory techniques, such as electron microprobe (for chemical composition analysis) and X-ray diffraction (for crystal structure determination). In field and collector conditions, it is impossible to identify due to the microscopic size of the grains and its occurrence as inclusions. ## Distinguishing from similar minerals Its unique chemical composition and crystal structure, confirmed by analytical methods, distinguish it from other minerals of the sapphirine supergroup and from other black, opaque oxide and silicate minerals. ## Crystal forms Devilliersite forms very fine, anhedral (not showing their own faces) grains up to 100 µm in size, occurring as inclusions within larnite crystals.
Geological environment
## Genesis Devilliersite forms under specific conditions of pyrometamorphic (high-temperature, low-pressure) metamorphism. Its occurrence is associated with rocks of the Hatrurim Formation, which formed as a result of the combustion of underground bituminous deposits, leading to the "burning" of surrounding carbonate rocks at temperatures exceeding 800°C. ## Mineral associations This mineral coexists with other rare minerals typical of the Hatrurim Formation, such as larnite (in which it forms inclusions), brownmillerite, ye'elimite, mayenite, maghemite, hematite, and representatives of the perovskite group. ## Localities The only confirmed locality of devilliersite in the world is its type locality: Har Parsa (Mount Parsa) in the Hatrurim Basin, Israel.
Rarity
Extremely rare
For collectors
## Quality criteria Devilliersite is not a mineral available on the collector's market. Its value is purely scientific and related to its status as a new, extremely rare mineral. The only existing specimens (type material) are held in the collections of research institutions, such as the Natural History Museum in London. The scientific value of a specimen depends on the possibility of its unambiguous identification and its association with other minerals from the paragenesis.
Care and storage
## Cleaning Due to its extreme rarity and microscopic mode of occurrence (as inclusions in other minerals), devilliersite specimens are not subject to cleaning under collector conditions. Any research and cleaning of type material are carried out exclusively in laboratory conditions using specialized equipment. ## What to avoid Mechanical and chemical cleaning methods that could damage not only devilliersite itself but, above all, the host mineral (matrix) should be avoided. Specimens should be protected from abrasion, chemicals, and extreme temperatures. ## Storage Samples containing devilliersite, being valuable research and type material, should be stored under stable conditions, in specialized containers protecting against dust, moisture, and mechanical damage. These are typically collections of scientific institutions.