Rakovanite

{{infobox mineral | name = Rakovanite | category = Pascoite family | boxwidth = 330px | boxbgcolor = | image = Rakovanite.jpg | imagesize = | alt = | caption = Well formed rakovanite crystals from the type locality: Sunday Mine, Slick Rock Mining District, San Miguel County, Colorado. | formula = (NH3)3Na3 [V10O28]12H2O | IMAsymbol = Rkv<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> | molweight = | strunz = 8.CJ.45 | dana = 40.4.7.4 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''P''2₁/n | unit cell = a = 12.0248(17), <br/>b = 17.121(3), <br/>c = 18.140(3) Å, <br/>β 106.242(8)°; Z&nbsp;=&nbsp;4 | color = Orange | streak = Orange-yellow | habit = Blocky to prismatic on [100] | cleavage = | fracture = Conchodial | tenacity = Brittle | mohs = 1 | luster = Subadamantine | diaphaneity = Transparent | gravity = 2.407 (calculated) | density = | polish = | opticalprop = Biaxial (+) | refractive = α_589nm = 1.776(5)<br/> β_589nm = 1.803(5)<br/> γ_589nm = 1.910(6) | birefringence = δ = 0.134 | other=Surface relief: very high<br>Orientation: X + b; Z Λ c= 8° in obtuse β<br> It does not fluorescence in long- or short-wave ultraviolent radiation.

| pleochroism = X light yellow, Y orangish yellow, Z yellowish orange, Z > Y> X | 2V = 2Vz_540nm =58(1); 2Vz_589nm = 56(1); 2Vz_650nm =53(1)° | dispersion = r < v, strong parallel | absorption = | melt = | fusibility = | diagnostic = | solubility = | alteration = | references = <ref>{{Cite web|title = Rakovanite: Rakovanite mineral information and data.|url = http://www.mindat.org/min-40447.html|website = www.mindat.org|accessdate = 2015-12-01}}</ref><ref name="Kampf" />}}

'''Rakovanite''', (NH₄)₃Na₃(V₁₀O₂₈) · 12H₂O; formerly given as Na₃(H₃V₁₀O₂₈)^.15H₂O; later, the ammonium ion was shown to be present and essential,<ref name=":0">{{Cite journal |last1=Kampf |first1=Anthony R. |last2=Hughes |first2=John M. |last3=Cooper |first3=Mark A. |last4=Hawthorne |first4=Frank C. |last5=Nash |first5=Barbara P. |last6=Olds |first6=Travis A. |last7=Adams |first7=Paul M. |last8=Marty |first8=Joe |date=2021-07-01 |title=The pascoite family of minerals, including the redefinition of rakovanite |url=https://pubs.geoscienceworld.org/canmin/article/59/4/771/607498/The-pascoite-family-of-minerals-including-the |journal=The Canadian Mineralogist |language=en |volume=59 |issue=4 |pages=771–779 |doi=10.3749/canmin.2000082 |bibcode=2021CaMin..59..771K |issn=1499-1276|url-access=subscription }}</ref> is a member of the pascoite family. It is a transparent, brittle mineral occurring in the monoclinic crystal system. It is orange in color and has an orange-yellow colored streak. Rakovanite is soft with a Mohs hardness of 1 and a calculated density of 2.407g cm⁻³. It does not fluoresce in long- or short-wave ultraviolet radiation. Rakovanite crystals are up to one mm in maximum dimension and vary in habit from blocky to prismatic on [001], commonly exhibiting steps and striations parallel to [001]. Its name honors John Rakovan, former professor, Department of Geology and Environmental Earth Science, Miami University,<ref name="Kampf">{{Cite journal|title = Rakovanite, Na₃V₁₀O₂₈•15H₂O, A New Member of the Pascoite Family with a Protonated Decavanadate Polyanion|journal = The Canadian Mineralogist|pages = 595–604|volume = 49|issue = 2|doi = 10.3749/canmin.49.2.595|first1 = A. R.|last1 = Kampf|first2 = J. M.|last2 = Hughes|first3 = J.|last3 = Marty|first4 = M. E.|last4 = Gunter|first5 = B.|last5 = Nash|year = 2011}}</ref> State Mineralogist and Senior Museum Curator, [https://geoinfo.nmt.edu/index.html New Mexico Bureau of Geology and Mineral Resources].

== Occurrence == Rakovanite was found on specimens from the Sunday mine and the West Sunday mine, Slick Rock district, San Miguel County, Colorado, US.<ref name="Kampf" />

It occurs as crystalline crusts on sandstone fractures in the mine walls of the Sunday and West Sunday mines. The best crystals were found perched on an amorphous dehydrated vanadium phase along with crystals tightly adhered to a corvusite-montroseite matrix.<ref name="Kampf" />

It forms from the oxidation of montroseite-corvusite assemblages. It is associated calcite, corvusite, hewettite, hughesite, montroseite, munirite, paramontroseite, pascoite, rossite, sherwoodite, and other unidentified vanadium phases as well as at least two other potentially new decavanadate species. It forms aqueous solutions of relatively low pH when water reacts with pyrite in the deposit under ambient temperatures and generally oxidizing near-surface environments.<ref name="Kampf" />

==Atomic arrangement== Rakovanite crystal unit consists of the decavanadate polyanion similar to that found in other decavanadate-bearing mineral. The decavanadate polyanion is formed of ten distorted, edge-sharing octahedra.<ref name=":0" />

==Chemical composition== {| class="wikitable" |- ! Oxide !! wt% !! Normalized wt% |- | Na₂O || 8.08 (0.35) || 6.90 |- | K₂O || 0.25 (0.02) || 0.21 |- | (NH₄)₂O|| 6.03 (0.42) || 7.09 |- | CaO || 0.03 (0.01) || 0.03 |- | V₂O₅|| 79.9 (0.56) || 70.08 |- | Al₂O₃ || 0.05 (0.01)|| 0.04 |- | H₂O || || 16.65 |-

| Total || || 100.00 |}

The empirical formula with calculated H₂O and (NH₄)₂O contents is [(NH₄)_2.94K_0.06]_Σ3.00(Na_2.97Al_0.01 Ca_0.01)_Σ2.99[V₁₀O₂₈]12H₂O (–0.01 H for charge balance) and the ideal formula is (NH₃)₃Na₃ [V₁₀O₂₈]12H₂O. <ref name=":0" />

==See also== {{Portal|Earth sciences}} * Classification of minerals * List of minerals * [https://www.mindat.org/min-40447.html Rakovanite on Mindat]

==References== {{Reflist|30em}}

Category:Oxide minerals Category:Monoclinic minerals Category:Minerals in space group 14