1,721,108 research outputs found
Studi sui minerali del Lazio: la kalistrontite di Cesano
No full textViene descritto il primo ritrovamento di kalistrontite in Italia. Il minerale, rinvenuto in un campione di carota proveniente da quota -1665 m del sondaggio RC1 effettuato dall'ENEL nell'area di Cesano (Valle del Baccano), e' associato ad anidrite e calcite ed e' ricoperto da minutissimi cristalli di celestina. I parametri di cella sono: a=5,447(1), c=20,857(6); la Dx=3,32, mentre la densita' sperimentale Dsper=3,28(1). Le sintesi effettuate dimostrano che la kalistrontite si forma in condizioni di eccesso di ioni K+
Insegnare Mineralogia
No full textViene descritta un'esperienza didattica effettuata nel corso universitario di Mineralogia che si potrebbe trasferire, opportunamente semplificata, al mondo della scuola per insegnare una disciplina che, a torto o a ragione, viene considerata la più difficile tra le Scienze della Terra
Refinement of the crystal structure of arsenolite, As2O3
No full textAs2O3, cubic, Fd (3) over barm (No. 227), a = 11.07343(5) Angstrom, V = 1357.8 Angstrom(3), Z = 16, R(P) = 0.056, wR(P) = 0.073, R(I) = 0.068, T = 295 K
Thermal and shock metamorphic features and terrestrial weathering in opaque minerals of some Antarctic ordinary chondrites recovered by Italian expeditions to Frontier Mountain
No full textWe studied opaque phases present in twenty-five H-chondrites, two L-chondrites and two LL-chondrites recovered by Italian Expeditions to Frontier Mountain. Petrologic types varying from 3 to 6 according to Van Schmus & Wood (1967) and shock stages ranging from S1 to S5 according to Stoeffler et al. (1991). Weathering effects in ordinary chondrites were also studied through reflected light microscopy. Shock features in opaque phases were compared to shock effects on silicate minerals. Physical changes in troilite and kamacite, studied in L-group ordinary chondrites, are present also in H-chondrites. Our study completes Bennett & McSween (1996) research and extends their shock classification based on textural and mineralogical variations of the opaque phases to the H group ordinary chondrites
Mineralogical characterization of the blue pigment of Michelangelo’s fresco “The Last Judgement”,
No full textThe blue pigment and the plaster layer of Michelangelo s fresco The Last Judgment have been characterized by means of powder XRD, FT-IR, and Raman spectroscopy, as well as analytical TEM and SAED. The pigment is composed of a mineralogical assemblage that is consistent with a raw lapis lazuli rock. To try to define ne the provenance of this pigment, we investigated various lapis lazuli
samples from different deposits that are currently considered as possible sources of the material. According to our results, the provenance of the pigment is quite dubious but the Pakistani one seems the most probable
The crystal structure of a "disordered" cancrinite
No full textlAn X-ray single-crystal structural investigation on a sample of cancrinite of formula Na7.13Ca0.87(Si6Al6O24) (SO4)(0.07)(CO3)(1.43) . 2H(2)O has been carried out. The cancrinite cage content has been found to be similar to that reported in previous structure refinements on natural and synthetic samples. However, differently from reference data, cations located inside the uninterrupted channel are distributed between two independent sites M1 and M2. Moreover carbonate groups are distributed, with partial occupancy, between two different z elevations (C1-OC1 and C2-OC2). The tetrahedral co-ordination of the sulphate group is obtained by partial substitution of carbon atoms at C1 and C2 by sulphur and oxygen. Two possible orientation with the apical oxygen pointing "down" or "up" are possible
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