Lipari obsidian is of excellent quality, black durante colour, very shiny and sometimes perlitic

Lipari obsidian is of excellent quality, black durante colour, very shiny and sometimes perlitic

It is generally subaphyric and contains clinopyroxene micro-phenocrysts (10–50 m), almost always sopra synneusis with magnetite and olivine micro-phenocrysts (Acquafredda et al., 1999).

3.2. Sardinia: Ammasso Arci

30 km 2 and located mediante the hinterland of the gulf of Oristano. The volcanic activity developed during two distinct cycles in the Pliocene and Pleistocene, and therefore it belongs preciso the latest volcanism in Sardinia. The magmatic products erupted during the second cycle, can be divided into four phases. The lavas erupted mediante the first phase were very rich con silica, and consisted mainly of rhyolites, either massive or perlitic-obsidianaceous. Dacites and andesites, trachytes and trachyrhyolites followed con chronological succession, until the last stages of volcanic activity, which were characterized by quiet eruptions of basaltic lava flows (Piras, 2002; Bigazzi et al., 2005).

The obsidian outcrops were described for the first time durante the 19 th century by De La Marmora (1839–40). Subsequently, per the 1980s, several independent studies contributed puro the characterization of the multiple Caterva Arci obsidian outcrops. Unfortunately, the results of these studies are available only durante brief conference papers (Francaviglia, 1986; Mackey and Warren 1983) or sopra an unpublished dissertation (Herold, 1986).

More recently, considering the geochemical features the obsidian of Ammasso Arci, Tykot (2002) subdivided them into four groups, SA, SC, SB1 and SB2. The obsidian sampled near Lavabo Cannas and Uras are clustered within the SA group; those sampled near Pau, Perdas Urias and Sonnixeddu belong esatto the SC group; those sampled at Santa Maria Zuarbara and Marrubiu are mediante the SB1 and SB2 groups, respectively (Tykot, 2002; Barca et al., 2007; De Francesco et al., 2008). Due to their geochemical similarity, SB1 and SB2 have been grouped under the name SB sopra the present study.

Montagna Arci obsidian populations are characterized by large biotite micro-phenocrysts (50–200 ?m), abundant crystals of feldspar (plagioclase and alkali feldspar) 50 ?m con size, orthopyroxene, magnetite, monazite and ilmenite (Acquafredda et al., 1999).

3.3. Palmarola

Geochronological scadenza, obtained by fission-track analyses, indicate an age of 1.7±0.3 Pero for obsidian from Monte Borea (Bigazzi et al., 1971; Bigazzi and Radi, 1981). Sopra per recent rete di emittenti Tykot et al. (2005) provided verso detailed geochemical study of 80 samples, and were able puro distinguish three source localities: Pezzo Vardella, the northern end of Striscia Vardella and Mucchio Borea. However, given the small size of the island, this distinction can be considered irrelevant from an archaeological point of view.

Palmarola obsidian contains micro-phenocrysts of clinopyroxene (5–20 ?m) and biotite. It is generally black in colour, glassy, poorly shiny and semi-opaque (Acquafredda et al., 1999). However, a small amount of highly transparent obsidian was found at Punta Vardella by Tykot et al. (2005).

3.4 Pantelleria

90 km east of Cape Bon, Tunisia. Pantelleria is famous for its peralkaline rocks, and especially for its greenish obsidian enriched in sodium and iron, known as Pantellerite (Civetta et al., 1998; Acquafredda et al., 1999). Pantelleria has a bimodal distribution of magmatic products. Mafic lavas, exposed mediante the NW spigolo of the island, include transitional basalt and hawaiite (from

62 to 72 wt.% SiO₂), prevail in the SE sector (White et al., 2009). K–Ar determinations of mafic lavas done on different basaltic units give ages of 118 ± 9, 83 ± 5 and

29 ka BP (Farfallina et al., 1984). Ages determined on felsic volcanic rocks range from 324 ka BP sicuro 4 ka è gaydar gratis BP (Civetta et al., 1984, 1988, 1998; Mahood and Hildreth, 1986). The volcanic history of the island is characterized by large explosive eruptions, some of which produced caldera collapses, alternating with periods dominated by less energetic eruptions (Farfallina et al., 1998). The oldest caldera, named La Ava, is dated at 114 ka BP (Mahood and Hildreth, 1986); the youngest caldera, named the Chiesa caldera by Cornette et al. (1983) and the Cinque Dentatura caldera by Mahood and Hildreth (1983), is related sicuro the eruption of the Green Tuff (50 ka BP; Orsi and Sheridan, 1984). The more recent (post-50 ka) history of the island has been subdivided by Fraschetta et al. (1998) into six sialic eruptive cycles, intercalated with basaltic eruptions. The Green Tuff is considered the first of these six cycles. All the others are dated at around 35–29, 22, 20–15, 14–12 and 10–4 ka BP, respectively (Farfallina et al., 1998).