MINING GREECE – GEOPARK OF MILOS – 001Milos: A geologist’s paradise

Milos literally rose up out of the Aegean Sea following earthquakes, tsunamis and submarine volcanic eruptions. All these natural phenomena occurred in the course of geological eons as a result of the collision and submersion of the African beneath the Euroasian continental plate (or Aegean plate). Approximately 3.5 to 2.7 million years ago, due to the collision of the aforementioned continental plates, a centre of volcanism was created in the Aegean (the volcanic arch that starts from Methana-Poros, continues to Milos and Santorini and concludes in Kos and Nisyros). At the same time, the first, massive volcanic eruption occurred, the centre of which was probably on the north side of Milos, followed by a sequence of eruptions.

As an island of volcanic origin, Milos has a very distinctive geology, meaning that the rocks and minerals of its soil and subsoil are related to its special creation. Some rocks and minerals of the island are very characteristic and owe their origin to volcanic processes.

Gases blasted through molten rocks form lava froth. When this froth cools very quickly, containing myriads of gas bubbles, it forms pumice. In Milos, the pumice layers were not flattened, while still hot, by the weight of overlaying rocks to be compressed into dense rock, but remained very soft for thousands of years. It is the pumice ash that Miloans have been using to create rock-cut shelters (storage areas, garages etc.), the well-known «syrmata», in various sites, such as Adamas, Klima, Mantrakia etc. Even the famous underground catacombs in Trypiti vilage have been dug in this soft pumice ash.

The result of the very quick cooling of lava, so that crystals do not have the time to be formed, was obsidian. Rock crystals are the product of gradual cooling of molten rocks, therefore obsidian is an amorphous volcanic glass. This particular property of obsidian makes it break into curved fracture planes, turning it into an ideal raw material for the making of tools and weapons with extremely sharp cutting edges. The black, shiny obsidian of Milos was the main reason for the development of prehistoric trade (Stone and Bronze Ages) in the Aegean, the metropolis of which was Phylakopi, and main extracting sites (quarries) Nychia and Demenegaki.

Perlite is submarine lava cooled abruptly on the sea floor and contains large amounts of trapped water. The minerals’ main property of expanding when heated is due particularly to this fact, i.e. the evaporation of the trapped water. There are two perlite deposits on Milos island that date back to two distinctive geological periods. The older deposit is called the Halepa perlite (from Mavra Gremna to Hivadolimni and Agia Marina, see Route 1) and, since it is far less glassy than the other perlite deposits of the island, it has different swelling properties. The younger Milos perlite deposits were the result of the submarine volcanoes of Fyriplaka on the south, and Trahilas on the north. They are chemically unique, different from other Greek perlites and of superior quality to the perlite at Halepa, due to their highly glassy structure and large water amounts that make them particularly light when expanded.

The clay minerals bentonite and kaolinite inform us whether the volcanic fluids were alkaline or acid: bentonite on Milos was formed by the leaching of porous, fragmentary rocks by seawater mixed with hot volcanic, alkaline waters. When the same porous rocks were also leached by hot, acid fluids, a blanket of kaolinite was deposited on the earlier bentonite. The bentonite of Milos is of very high quality. Three distinct groups of bentonite appear on Milos with slightly different properties: the deposits of Zoulias- Aspro Horio-Tsantili, the largest deposit of Angeria and Koufi, and finally the deposits of Ano and Kato Komia, Rema and Mavrogiannos. Greece is the second largest producer of bentonite after USA. Most of the country’s production comes from Milos.

The volcanic activity on Milos produced hot underwater volcanic fluids, rich in metals that found their way to the surface through fractures. The cooling of these fluids as they were moving up towards the surface resulted in deposits of metals along their way. This can be best seen in the old manganese mines at Cape Vani, on the northwestern part of Milos.

Barite was created in a similar way on Milos: as the hot, metal-rich fluid moved up through the open fractures, it met cold, sinking seawater. This mixing resulted in the precipitation of barium sulphate (barite) in the fractures. Such deposits can be seen along old fractures at Triades and Komia in the Voudia area, and in former times, barite deposits were mined.

The Milos Sulphur Mine at Paliorema, on the south coast of the island, was one place where there was a downward streaming of extremely acid warm water. A natural passage of about 70 m. in diameter was used by hot waters, which ascended, and leached almost everything out of the original volcanic rocks. The same passage was used for the descent of warm waters, rich in sulphuric acid, filling the cavities and pores with yellow native sulphur. Paliorema still smells of sluphuric acid.

Visit the MILOTERRANEAN GEO EXPERIENCE website ( ) and find out everything about the mining history of this beautiful Greek island


MINING GREECE – GEOPARK OF MILOS – 002Miloterranean Geo Walks

Thanks to its volcanic grounds and its magical geographic bas-relief, Milos is a natural geologic park ready to be explored.

For all those interested in such an extraordinary tour, the Mining Museum of Milos organizes geo walks to the most important locations of geological and mining interest on the island. (For more information visit: or call at tel.: 0030 22870 21620).

We recommend the following footpaths that present a geological and mining interest:

Route A’

  • “Milos Conference Center -George Eliopoulos”

The building used to be a plant for the processing of kaolin. It was renovated by the company ORYMIL S.A. It is in full operation since 2000.

  • Kanavas Factory

It is a factory for the processing of bentonite and port installations for loading, owned by the company S&B Industrial Minerals S.A.

  • Kanavas Fumaroles

Submarine leaks of hot gasses and the gushing of hot water of a temperature 35-75C. They are used as hot springs.

  • Alyki Salt works

Old salt production facilities where salt was produced through the natural evaporation of seawater.

  • Alyki Spa

Ancient spa cave. Chlorinated hot spring waters.

  • Geothermic Plant

A plant for the production of electric power having as motive power the pressure of the geothermic liquids in the area that used to rise to the surface by P.P.C. drillings. It functioned experimentally for a limited time period and it was abandoned mainly due to technical reasons.

  • Fylakop i- Papafragas

The development of Fylakopi, the prehistoric settlement of Milos, according to many researchers is attributed to the trading of obsidian. Papafragas is a small sandy beach that was created by volcanic tuffs having as main component the fragments of pumice (pumice-stone).

  • Zefyria or Hora

A medieval city of Milos. It flourished till the end of the 17th century. The inhabitants abandoned the city because of the volcanic fumes and the epidemics. In the area there is one of the world’s best geothermic fields.

  • Installations of the company S&B Industrial Minerals S.A., Voudia

Here, in 1934, the Company began its activities on Milos with the aim to exploit silver and barite. In 1950s the processing of bentonite, kaolin and pearlite began. Today there are modern installations for the processing of pearlite and bentonite, of the biggest ones in Europe. From the loading bridge 95% of the production is exported worldwide.

  • Aggerias Mine

One of biggest bentonite mines in the world. The exploitation began in 1985 and the average annual mining is one million tons. The different colors that can be seen are due to the different material quantities and they are created by the iron oxides.

Route B’

  • Sarakiniko

A volcanic formation, the shape is mostly caused by the sea erosion and the rainwater. The presence of sea fossils is obvious.

  • Fyropotamos

A plant for the processing of the mineral kaolin in the 1960s.

  • Trahilos

Remnants of volcanic activity.

A pearlite mine of the company S&B Industrial Minerals S.A., where the simultaneous exploitation and restoration of the landscape takes place (restored gradients by the sea).

Route C’

  • Hivadolimni

An old pearlite mine restored by the company S&B Industrial Minerals S.A.

  • Tsigrado

A plant for the production of pearlite owned by the company S&B Industrial Minerals S.A.

  • Fyriplaka crater

Remnants of the last volcanic activity on the island.

  • Kalamos

A characteristic sample of fumaroles’ action on the island. The overheated steams are released by wheezing from the underground leaving accretions of salts and sulphur.

  • Aghia Kyriaki

Traces of mineral activity in the period of classical antiquity era and in the Roman era.

Other Important Sights

  • Glaronisia

Andesitic lava. Characteristic columnar splitting with pillars of mainly pentagonal segmentation, indicative of the freezing in minor depth.

  • Kleftiko

White tuffs of a characteristic stratification. The pirates used it as a refuge.

  • Vani

A slow mine for the exploitation of manganese which is of important geological interest.

  • Demenegaki

Prehistoric obsidian mines

  • Sulphur mines (Theioryhia)

Deserted mining tunnels and a plant for the processing of sulphur.

Milos Mining Museum

The Mining Museum of Milos, an urban non-profitable company, was established by S&B Industrial Minerals S.A. in 1998 with the aim to honor and promote the mining history as well as the geological and natural heritage of Milos.

On the ground floor there is an exhibition of the social, financial and technological aspects of Milos’s mineral history and tradition, which is dedicated to the island’s natural and geological wealth. The minerals used to be mined on the island since the Neolithic age and are presented all the way to the present day; special emphasis is given on their usage in our everyday life. What is more, there is a room equipped with audiovisual means to project videos on the mineral extraction and production process where visitors can “travel” back to older periods through the descriptions of old miners.

The Museum organizes special guided geo walks, whereas in its premises several educational programs take place and pedagogic and recreational activities are organized in cooperation with skilled educational carriers and museum-educators. In its 12 years of operation, the Museum has been visited by more than 135,000 people from Greece and abroad, whereas it has become a favorite destination of educational tourism.

Additional Info

Opening Hours: 1 June – 30 September: 9:00 – 14:00 & 17:00 – 20:30 daily, October, April & May: 9:30 – 14:00 & 17:30 – 20:30 daily, 1 November – 31 March: Saturday 9:00 – 14:00, Sunday to Friday upon advance notice.

Admission: 3€ (2€ for people over 65 years old, Free admission for children under 10 years old and students

Area: Adamantas

Phone: + 30 22870 22481

Fax: +30 22870 23984



Sulphur Mines

On the eastern part of the island lies Paliorema, a bay with crystal clear emerald waters and yellowish pebbles, colored by the sulphur of the area. There the sulphur mines of Victor Melas used to be in operation, the oldest ones in Greece.

In Paliorema or Theioryheia you can combine your swim with a visit to one of the geological sites of the island’s mining history. You can rest on the beach with the colorful pebbles and the fine sand and you can enjoy your swim viewing the old quarries for the mining of sulphur and the ruins of offices, spare parts and personal items of the quarries’ workers which compose an attractive landscape.

Historically, between 1890 and 1905, the mines had been in operation, owned by the Company of Public and Municipal Works. In 1905 the mines were forced to stop operating due to the production of sulphur at low prices in the U.S.A. In 1910-1918 they operated sporadically, whereas in the 1930s they were in full operation and the facilities of at that time can be seen even today. The sulphur mines, the Theioryheia, were in operation until 1960, whereas their business activity ceased to be carried on permanently in 1978.