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This work relates the occurrence and the characterization of fibrous tremolite within the latest pyroclastic deposits of the Colli Albani (Alban Hills) volcano, to the south-east of Rome (Italy). These mineralizations were observed during a systematic rock sampling undertaken to complete the geological survey for the new 1:50,000 map of this volcanic area. The examined specimens were collected inside distal deposits correlated to the last Albano Maar activity, which are geographically located within the boundaries of the Nemi community. Tremolite occurs within both carbonate ejecta and the host pyroclastic rocks. It shows up as whitish to light grey-coloured aggregates of crystals with fibrous aspect and sericeous brightness. Due to the extremely small crystal dimensions, never exceeding 0.5 mu m in diameter, the micro-chemical composition of the fibres could be obtained only by combining P-XRD, SEM-EDX and FTIR methods. Infrared spectroscopy, in particular, proved to be a valuable technique to characterize the studied amphibole. The composition determined is that of a Fe-free F-rich (c. 53 %) tremolite with significant (c. 20 %) richterite components in solid solution. The occurrence of fibrous tremolite in an inhabited place, occurring as natural geological material rather than being due to anthropogenic pollution, should be examined with concern, because it implies complex health and legal responsibilities in the case of mobilization due to extreme climatic events.

All updated data of scientific and historical interest on the 15 mineral species first described in Rome and in the surrounding area i.e., from lake Bracciano, to the North, to lake Nemi, to the South, are assembled and discussed. Their typical morphologies are also presented as photographs. In addition, a full list of all minerals described over the area is given. A distinction is made between minerals occurring as euhedral, conspicuous crystals and those present as rock forming grains. Most minerals are discussed with reference to their significance for establishing the pressure and temperature conditions at which they formed, with special attention for those occurring in the lavas and pyroclastics related either to the Sabatini volcanic complex or to the Alban Hills volcano, both belonging to the world-renowned Roman Comagmatic Region. The few sedimentary minerals of palaeomagnetic and geothermal significance in the Tiber valley and in ancient lakes and ponds scattered through the Roman campaign are also listed and briefly discussed.

Uno dei maggiori problemi nel restauro o nella gestione dei Beni Culturali è l'analisi non distruttiva dei materiali costituenti il manufatto, litoidi o non, che e volte deve essere effettuata senza la distruzione di frazioni anche piccolissime, o, in casi estremi, senza nessuna manipolazione dell'oggetto di cui si desidera conoscere la natura o la composizione. Un esempio di quest'ultimo caso è rappresentato dall'analisi dei marmi della Pietà Rondanini e di un frammento recentemente ritrovato (Mantura, 1973) e conservato presso la galleria Borghese raffigurante la testa e una spalla del Cristo, attribuito alla stessa Pietà, di dimensioni di circa 60 cm. All'osservazione macroscopica, il marmo con cui erano stati ottenuti i due manufatti sembrava essere lo stesso, ed una loro diversificazione poteva essere effettuata, al di fuori di ogni ambiguità, solo attraverso un esame di qualche caratteristica microscopica o microchimica peculiare del materiale. Tale problema poteva essere risolto solo attraverso una analisi della roccia con cui i due pezzi erano stati ottenuti, ma qualunque tipo di analisi analisi avrebbe comportato una seppur piccola manipolazione del pezzo, e questo non era possibile. A questo punto si è pensato di sfruttare una proprietà fisica particolare dei materiali geologici: la radioattività.

Non-metamict betafite, a pyrochlore-group mineral with general formulaA2−mB2XO6Y(O,OH,F)1−n·pH2O and 2 Ti > Nb+Ta and U > 20% at theAsite, has been found at Le Carcarelle, (Latium, Italy). It occurs within miarolitic cavities of a foid-bearing syenitic ejectum enclosed within the pyroclastic formation known as “ignimbrite C”, which belongs to the main effusive phase of the Vico volcanic complex. The host rock is composed of K-feldspar, biotite, augitic clinopyroxene, magnetite and minor sodalite. Electron microprobe analyses gave the following crystal-chemical formula: (Ca1.24Na0.17U0.49REE0.03)Σ=1.93(Ti1.05Nb0.76Zr0.14Fe0.04Ta0.01)Σ=2.00O6(O,OH). Compared with other occurrences reported in the mineralogical literature, betafite from Le Carcarelle is extremely enriched in U and depleted in Th. Due to its young age of formation (∼150 k.y.), this betafite sample is highly crystalline, thus allowing structure refinement of unheated material. Betafite from Le Carcarelle is cubicFdm, witha= 10.2637(13) Å, andV= 1081.21(35) Å3, and has a smallerAsite (consistent with the higher U content), and a larger and more distortedBsite (consistent with the higher Ti content) than calciobetafite from Campi Flegrei, Italy (Mazzi and Munno, 1983). Analysis of the atomic displacement parameters provides evidence for static disorder at theXsite.

La vanadinite si ritrova all’interno delle cavita miarolitiche di un proietto sienitico raccolto a Monte Cavalluccio, sul bordo nord della caldera di Sacrofano, nel complesso vulcanico dei monti Sabatini. La vanadinite si presenta sotto forma di sferule bianco-giallastre di aspetto terroso formate da cristalli aciculari. Le dimensioni di cella raffinate con i minimi quadrati sono:a(A)=10.269(7),c(A)=7.349(8),V(A3)=671.2. La formazione della vanadinite e secondaria alla formazione della roccia ospitante ed e opera di fluidi tardivi. Probabilmente essa avvenne successivamente alla emissione dell’unita piroclastica contenente il proietto.