The Monte Arci is an isolated massif in the Uras

Uras

For the Sumerian goddess see UrasUras is a comune in the Province of Oristano in the Italian region Sardinia, located about 60 km northwest of Cagliari and about 25 km southeast of Oristano...

 plain in Campidano

Campidano

Campidano is a plain located in the south-western area of Sardinia, Italy, covering approximately 100 kilometres between Cagliari and Oristano....

, Sardinia

Sardinia

Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. It is composed by three volcanic basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 towers, the highest one reaching an elevation of 812 m. The inner part of the massif is composed of trachyte

Trachyte

Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present....

.

Monte Arci had a relevant historical role in Sardinia due to the abundant presence of obsidian

Obsidian

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...

, which was used since prehistoric times for weapons and tools, and was later traded outside the island. There are also quarries of pearlite

Pearlite

Pearlite is often said to be a two-phased, lamellar structure composed of alternating layers of alpha-ferrite and cementite that occurs in some steels and cast irons...

. In the territory of Morgongiori

Morgongiori

Morgongiori is a comune in the Province of Oristano in the Italian region Sardinia, located about 70 km northwest of Cagliari and about 25 km southeast of Oristano on the southern slopes of Monte Arci....

 there are breeds of Giara horses.