Cavansite – Electric Blue Crystal Rosettes on Stilbite...

Cavansite – Little blue stars among the white crystals of India. Mineralogical specimen from India, characterized by numerous small crystals of deep blue cavansite distributed on a matrix covered with white crystals, lamellar and fibrous in appearance, plausibly attributable to zeolites. The specimen presents a particularly recognizable color association: on the ivory-white surface, pierced by pearly and translucent reflections, numerous aggregates of brilliant blue emerge, with shades ranging from turquoise to intense cyan blue. Observing the photographs, small radial formations are distinguishable, some resembling stars, others gathered into tiny tufts or rosettes. These structures consist of cavansite crystals developed in divergent aggregates. Their distribution is irregular: some crystallizations are isolated on the surfaces of the white crystals, while others concentrate in the interstices and small cavities of the matrix. Cavansite is a rare hydrated calcium-vanadium silicate, described as a new mineral species in 1967. Its name derives from the combination of the symbols of the main elements of its chemical composition: calcium (Ca), vanadium (V), and silicon (Si). The chemical formula is Ca(VO)Si4O10·4H2O. The blue color is linked to the presence of vanadium in the crystal structure. Unlike many minerals whose color is due to trace impurities, in cavansite vanadium is an essential component of the chemical composition. The best-known samples come from cavities in basaltic rocks of Maharashtra, in western India. In this region, the ancient Deccan lava flows have developed fracture and cavity systems in which, during successive stages of mineralizing fluid circulation, several associations of secondary minerals formed. Cavansite frequently occurs together with minerals from the zeolite group, including stilbite. These latter can develop tabular, lamellar crystals or aggregations in fan-like formations, offering surfaces on which the small blue crystals form. In the photographed specimen, the matrix presents a complex texture, with overlapping white crystals oriented in different directions. Some are elongated and thin, others show wider terminations and surfaces slightly pearly. Among these elements, cavansites insert themselves, often developed directly on the pale crystals."

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