Summary
Zincoberaunite is an iron and zinc phosphate mineral, the Zn analogue of beraunite. It was first described by Chukanov et al. for an occurrence in Hagendorf Sud pegmatite in Germany.[3] Zincoberaunite occurs as a secondary mineral as an alteration product of primary phosphate minerals in granite pegmatites.
| Zincoberaunite | |
|---|---|
| General | |
| Category | Phosphate minerals |
| Formula (repeating unit) | ZnFe3+5(OH)5(PO4)4·4H2O |
| IMA symbol | Zbru[1] |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Unit cell | a = 20.837(2) Å, b = 5.1624(4) Å, c = 19.250(1) Å; β = 93.252(5)° |
| Identification | |
| Color | Light gray, light greenish yellow |
| Crystal habit | Fiber, capillary or prismatic microcrystals |
| Mohs scale hardness | 3–4 |
| Luster | VSilky, vitreous |
| Diaphaneity | Translucent |
| Specific gravity | 2.94 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.745 nβ = 1.760 nγ = 1.770 |
| Birefringence | δ = 0.025 |
| 2V angle | Measured: 80° |
| References | [2] |
Beraunite crystallizes in the monoclinic crystal system with point group 2/m. Beraunite's formula is Zn Fe3+5(OH)5(PO4)4·4H2O.
Occurrence edit
Zincoberaunite has been located so far in two localities in the world, the type locality, and Krasno, near Horní Slavkov (Czech Republic). It appears in two paragenesis, as an alteration of other phosphates in pegmatites: in one with jungle, phosphophyllite and mitridatite and in another with flurlite, plimerite, beraunite rich in zinc, schoonerite, parascholzite, robertsite and altered phosphophyllite. However, it is likely that a detailed study of the zinc-rich beraunite specimens will allow locating other localities for the zincoberaunite.
Physical and chemical properties edit
Zincoberaunite contains Zn instead of ferrous iron. Before it was characterized as an independent species, specimens with a high zinc content had been found, but since the iron content was higher, they had been considered as varieties. In addition to the elements indicated in the formula, it contains small amounts of magnesium and calcium. In the type locality it appears as pale gray capillary microcrystals forming silky-looking aggregates. In a second locality it has been found as prismatic microcrystals with compositional zoning.[4]
References edit
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Mindat.org
- ^ Chukanov, N.V., Pekov, I.V., Grey, I.E., Price, J.R., Britvin, S.N., Krzhizhanovskaya, M.G., Kampf, A.R., Dünkel, B., Keck, E., Belakovskiy, D.I., MacRae, C.M. (2017). "Zincoberaunite, ZnFe3+5(PO4)4(OH)5⋅6H2O, a new mineral from the Hagendorf South pegmatite, Germany". Mineralogy and Petrology. 111 (3): 351–361. doi:10.1007/s00710-016-0482-y. S2CID 133425928.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Tvrdý, J., Plášil, J. Škoda, R. (2020). "New crystal-chemical data on zincoberaunite from Krásno near Horní Slavkov (Czech Republic)". Journal of Geosciences. 65: 45–57. doi:10.3190/jgeosci.296. S2CID 219082389.
{{cite journal}}: CS1 maint: multiple names: authors list (link)