Coquimbite, AlFe3+3(SO4)6(H2O)126H2O, was considered as a pure Fe3+ hydrated sulfate. However, previous mineralogical studies pointed out the occurrence of essential Al, occupying a distinct site in the crystal structure of this mineral. Through the critical re-examination of the available literature and new crystal-chemical data collected on a specimen from the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy, the chemical formula of coquimbite has been revised, taking into account the occurrence of Al. Coquimbite has a homeotypic relationship with paracoquimbite, Fe4(SO4)6(H2O)126H2O; both mineral species belong to the coquimbite group. On the contrary, aluminocoquimbite, Al2Fe2(SO4)6(H2O)126H2O, has a different topology and does not belong to that group.
Redefinition of coquimbite, AlFe3+3(SO4)6(H2O)126H2O
Mauro D.
;Biagioni C.;Pasero M.;
2020-01-01
Abstract
Coquimbite, AlFe3+3(SO4)6(H2O)126H2O, was considered as a pure Fe3+ hydrated sulfate. However, previous mineralogical studies pointed out the occurrence of essential Al, occupying a distinct site in the crystal structure of this mineral. Through the critical re-examination of the available literature and new crystal-chemical data collected on a specimen from the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy, the chemical formula of coquimbite has been revised, taking into account the occurrence of Al. Coquimbite has a homeotypic relationship with paracoquimbite, Fe4(SO4)6(H2O)126H2O; both mineral species belong to the coquimbite group. On the contrary, aluminocoquimbite, Al2Fe2(SO4)6(H2O)126H2O, has a different topology and does not belong to that group.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
