Kampf AR1, Rossman GR2, Ma C2, Belmonte D3, Biagioni C4, Castellaro F5, Chiappino L6

1 Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
2 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
3 Dipartimento per lo Studio del Territorio e delle sue Risorse, Università degli Studi di Genova, Corso Europa 26 - 16132 Genova, Italy
4Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, I-56126 Pisa, Italy
5 via XXV Aprile 28, I-16046 Mezzanego, Italy
6 via Palmanova 67, I-20132 Milano, Italy


Ramazzoite (IMA2017-090), [Mg8Cu12(PO4)(CO3)4(OH)24(H2O)20][(H0.33SO4)3(H2O)36], is a new polyoxometalate mineral from the Monte Ramazzo mine, near Genova, Liguria, Italy. It occurs on magnetite-rich matrix in association with chlorartinite, chrysotile, dypingite, goethite, lepidocrocite and nesquehonite, and is a late-stage, secondary mineral crystallizing from low-temperature, aqueous solutions. Ramazzoite forms as simple cubes up to about 0.15 mm on edge. The mineral is blue to greenish-blue with a vitreous to oily lustre and pale blue streak. Crystals are very brittle with conchoidal fracture, and a perfect cleavage on {100}. The Mohs’ hardness is 2½. The measured density is 1.98(1) g·cm-3. The mineral is soluble with mild effervescence in dilute HCl at room temperature. Optically, ramazzoite is isotropic with n = 1.491(1) (white light). Electron microprobe analyses gave the empirical formula [(Mg8.00)(Cu8.00Mg3.78)(PO4)(CO3)4(OH)24(H2O)20] [(H0.65S1.01O4)3(H2O)36], based on 1 P apfu. Ramazzoite is cubic, P-43m, with the unit cell parameters: a = 13.3887(10) Å, V = 2400.0(5) Å3 and Z = 1. The crystal structure, refined to R1 = 0.064 for 803 observed reflections [I > 2σI], contains a novel [Mg8Cu12(PO4)(CO3)4(OH)24(H2O)20]5+ polyoxometalate cation.

Ramazzoite, from the Monte Ramazzo Mine

IR spectrum
Infrared spectrum of ramazzoite in the water region