Castelnuovo Mine (Castelnuovo Pit; Castelnuovo deposit), Cavriglia, Arezzo Province, Tuscany, Italyi

Regional Level Types
Castelnuovo Mine (Castelnuovo Pit; Castelnuovo deposit)	Open-Cast Mine (Reclaimed)
Cavriglia	Commune
Arezzo Province	Province
Tuscany	Region
Italy	- not defined -

Open-pit mine of the Santa Barbara mining concession, situated near the village of Castelnuovo dei Sabbioni, opened in the homonymous lignite deposit in the period 1956-1994. It reached the depth of 150 m. Presently reclaimed.

The first mine, opened in 1864 in the Castelnuovo deposit, was an open-pit mine named Casino mine (Miniera del Casino). Later, the deposit was mined mainly by underground methods and included various mines such as the mines named Castelnuovo or Bicchierone, Cave Vecchie, Poggio d'Avene, Le Culle, Carpinete, Basi, and Valle al Pero. Castelnuovo's last underground mine, Carpinete (43.553163 N, 11.473551 E), closed in 1969.

The first mineral described for this lignite deposit is a white-yellowish fossil resin, found as small brittle blades, often grouped to form fibrous-radiating spherules, and incrustations in lignite. It was supposed a new species and named bombiccite (Bechi, 1868; Bombicci, 1869; and other authors). Studies performed by Boeris (1921) and Ciusa & Galizzi (1921) led to suppose the possible sameness between bombiccite and hartite, later confirmed by X-ray powder diffraction and single-crystal analyses performed by Pellizzer (1955 a,b). Detailed work concerning the hartite structure was subsequently published by Foresti Serantoni et al. (1978), who established this natural diterpene as having the alpha-dihydrophyllocladene structure.

Other minerals reported in the first period of mining activity are siderite and pyrite. Siderite was first noted by Grattarola (1876) as small crystals in lignite fissures. According to Sagri & Magi (1992), it can be found, both within Meleto Clays and the lignite layers, as lenses and nodules, and rarely as yellowish-brown euhedral microcrystals. Pyrite was found as small crystalline masses during the underground mining operations in stopes characterised by gaseous exhalation (Castelli, 1922).

The recent mining operations allowed to discover layered deposits of phosphates inside the Meleto Clays. Anapaite and vivianite were abundantly found, but always separately in different layers.
In particular, anapaite appears as radiating masses with variable shape and size. The interior contains many cavities filled by aggregates of triclinic tabular crystals. The crystals are green or yellow-green, translucent, vitreous, and a millimeter or two in size. A gradual change in the character of the masses, with regard to their position inside Meleto Clays, has been observed: in the uppermost part there are small nodules, nearly spherical and about 1 cm in diameter, progressing to nodules as large as 10 cm in diameter in the lower part. The anapaite nodules often appear joined together to form a compound cluster. At the bottom of the formation of Meleto Clays, near the Macigno Sandstone, layers of anapaite with a thickness ranging from 5 to 20 cm and an extension of tens of meters occur. Anapaite is rarely associated with baryte, as thin, radiating, hemispherical, yellowish aggregates no larger than 1 mm.
Vivianite most commonly occurs as a replacement of vegetable organic matter; blue to dark blue, perfectly preserved leaves have been collected in a bluish clayly matrix. The concretionary radiating nodules are also very attractive; they are blue, up to 7 cm in size and have cavities lined with bright blue vivianite crystals to 2 mm. Blue earthy concretions also occur.

Castelnuovo mine, is the type locality for grattarolaite and rodolicoite, two anhydrous iron phosphates, found as reddish-brown nodules in lignite beds which appear to have naturally burned. The two mineral species occur as small crystallites (<100 nm), associated in fine-scale intergrowth that prevent the measurement of physical properties.

Gypsum, as aggregates of greyish dull prismatic crystals, has been occasionally found in the bluish clays. However, the best specimens, consisting of colourless elongated crystals reaching several centimetres in length, have been found on a particular orange-red brick-like matrix, which formed during lignite self-combustion through clay baking and the consequent oxidation of ferrous minerals (Billi, 1980; Brizzi et al., 1991; Corazza et al., 1994).

Other Regions, Features and Areas containing this locality

References