Blossite

{{infobox mineral | name = Blossite | image = | alt = | caption = | category = Vanadate mineral | formula = {{chem2|CuV2O7}} | IMAsymbol=Blo<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | strunz = 8.FA.05 | dana = 38.5.6.1 | system = Orthorhombic | class = Pyramidal (mm2) <br/><small>(same H-M symbol)</small> | symmetry = ''Fdd2'' | unit cell = a = 20.676(6)&nbsp;Å, <br/>b = 8.392(3)&nbsp;Å, <br/>c = 6.446(2)&nbsp;Å; Z&nbsp;=&nbsp;8 | color = Black, white in reflected light, red-brown internal reflections | habit = Anhedral crystals and intergrowths | twinning = | cleavage = | fracture = | tenacity = | mohs = | luster = Metallic | streak = Red brown | diaphaneity = Opaque | gravity = 3.95 – 3.97 (measured on synthetic material) 4.05 (calculated) | density = | polish = | opticalprop = Biaxial | refractive = 2.05 | birefringence = Bireflectance: weak to moderate: cream-white shades | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = <ref name=Mindat>[http://www.mindat.org/min-697.html Blossite] on Mindat.org</ref><ref name=Webmin>[http://webmineral.com/data/Blossite.shtml#.UymYC6jMS1U Blossite data on Webmineral]</ref><ref name=HBM>[http://rruff.info/doclib/hom/blossite.pdf Blossite in the Handbook of Mineralogy]</ref> }} '''Blossite''' is an anhydrous copper vanadate mineral with the formula: {{chem2|Cu(2+)V(5+)2O7}}.<ref name=Krivovichev/> Blossite was named for mineralogist F. Donald Bloss of Virginia Polytechnic Institute and State University.<ref name=Robinson/>

==Natural and synthetic occurrence== Blossite was first described for an occurrence in the “Y” fumarole<ref name="The cooling of Izalco volcano" /> in the summit crater of Izalco Volcano, El Salvador.<ref name=Robinson/> There it occurs with several high-temperature minerals including: stoiberite, fingerite, ziesite, and mcbirneyite.<ref name=Robinson/> The natural analogues of these compounds crystallize in the CuO-V₂O₅ binary system first studied by Brisi and Molinari (1958) and were first discovered as synthetic compounds. Blossite is the low temperature polymorph of ziesite, β-Cu₂V₂O₇.<ref name=Robinson/> All of the blossite crystals identified to date are inter-grown<ref name=Robinson/> with other fumarolic copper vanadates. The discovered location of these copper vanadates, in the outer sulfate zone of the fumarole, indicates a sublimation temperature between 100&nbsp;°C and 200&nbsp;°C.<ref name="Fumarole incrustations at active Central American Volcanoe" />

==Physical properties== Blossite occurs as black anhedral crystals, with dimensions not exceeding 150&nbsp;um. Crystals of blossite have only been isolated with other fumarolic copper vanadates or sulfates. Blossite demonstrates a red-brown streak, prevalent to the natural copper present, this red-brown coloring is also a prevalent in the internal reflections. No cleavage is observed in blossite, but the size of the natural mineral grains of polycrystalline prohibit the identification of cleavage. In ultraviolet radiation blossite does not fluoresce, it demonstrates a white color when blue-filtered white light in air is present, and is opaque to transmitted light. The density of natural occurring blossite is 4.051&nbsp;g/cm³.<ref name=Robinson/>

==Composition== The chemical formula of blossite is, Cu₂²⁺V₂⁵⁺O₇.<ref name=Robinson/> 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%''.<ref name=Robinson/> Blossite is the only stable phase of the Cu₂V₅O₇ compounds at ambient conditions.<ref name=Krivovichev/> 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.<ref name=Krivovichev/> Blossite’s atomic structure is formed when three Cu-O bonds are broken during the phase change.<ref name=Robinson/> The phase transition is of the non-nearest-neighbor reconstructive type, relative high activation energy is required for the phase change.<ref name=Robinson/> Blossite is also formed when the fumarole temperatures are lower than inversion temperatures of {{convert|710|C}}.<ref name=Robinson/>

==Crystal structure== Blossite is part of the copper vanadates class, the V⁵⁺ form a tetrahedral coordination surrounded by oxygen atoms.<ref name=Robinson/> The VO₄ tetrahedra is closely related to thortvetite-group compounds by the formation of [V₂O₇]⁴⁻.<ref name=Robinson/> 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.<ref name=Robinson/> The independent copper cation in blossite forms as a polyhedral structure coordinated by five oxygen atoms forming an apically elongate square pyramid.<ref name=Krivovichev/> The shared edges of CuO₅ from chains that lay parallel to [011] and [011], this orientation is common in the three polymorphs of Cu₂V₂O₇.<ref name=Robinson/> Blossite structure represented in a block form by Krivovichev et al. represents two series of slabs with both lying perpendicular in orientation.

==References== {{Reflist|refs= <ref name=Robinson>Robinson, P.D., Hughes, J.M., and Malinconico, M.L. (1987) Blossite, α-Cu_2^2+V_2^5+O7, a new fumarolic sublimate from Izalco volcano, El Salvador. American Mineralogist, 72, 397–400</ref> <ref name=Krivovichev>[http://rruff.info/doclib/cm/vol43/CM43_671.pdf Krivovichev, S.V., Filatov, S.K., and Cherepansky, P.N. (2005) Crystal structure of γ-Cu2V2O7 and its comparison to blossite (α-Cu2V2O7) and ziesite (β-Cu2V2O7). Canadian Mineralogist, 43, 671–677]</ref> <ref name="Fumarole incrustations at active Central American Volcanoe">Stoiber, R.E., and Rose, W.I. (1974) Fumarole incrustations at active Central American Volcanoes.GeochimaetCosmochimicaActa, 38, 495–516.</ref> <ref name="The cooling of Izalco volcano">Stoiber, R.E., Rose, W.I., Lange, I.M., and Birnie, R.W. (1975) The cooling of Izalco volcano (El Salvador) 1964–1974. GeologischesJahrbuch, 13, 193–205.</ref> }}

Category:Copper(II) minerals Category:Vanadate minerals Category:Orthorhombic minerals Category:Minerals in space group 43 Category:Minerals described in 1987