Blossite

The chemical formula of blossite is, Cu₂²⁺V₂⁵⁺O₇.^[6] Robison et al. conducted quantitative analyses using an ETEC Autoscan microprobe operating at 20kv on a polished sample of blossite-fingerite intergrowth, the results of the oxide weight percentage. Chemical analysis V₂O₅ 53.28%, CuO 46.49% :Total 99.77%; Ideal chemical formula:V₂O₅ 53.34%, CuO 46.66%:Total 100%.^[6] Blossite is the only stable phase of the Cu₂V₅O₇ compounds at ambient conditions.^[5] The structure A2B2X7, is mostly associated with B= P and V, the B2O7 groups orient and fluctuate size based on the electronic structure of the A cation.^[5] Blossite’s atomic structure is formed when three Cu-O bonds are broken during the phase change.^[6] The phase transition is of the non-nearest-neighbor reconstructive type, relative high activation energy is required for the phase change.^[6] Blossite is also formed when the fumarole temperatures are lower than inversion temperatures of 710 °C (1,310 °F).^[6]

Blossite is part of the copper vanadates class, the V⁵⁺ form a tetrahedral coordination surrounded by oxygen atoms.^[6] The VO₄ tetrahedra is closely related to thortvetite-group compounds by the formation of [V₂O₇]⁴⁻.^[6] The [V₂O₇] planes lie along [100], the divanadate units are staggered orienting the V-OB-V vector parallel to [120] in one plane and parallel to [120] in the adjacent plane.^[6] The independent copper cation in blossite forms as a polyhedral structure coordinated by five oxygen atoms forming an apically elongate square pyramid.^[5] The shared edges of CuO₅ from chains that lay parallel to [011] and [011], this orientation is common in the three polymorphs of Cu₂V₂O₇.^[6] Blossite structure represented in a block form by Krivovichev et al. represents two series of slabs with both lying perpendicular in orientation.