## 1 Introduction  
Raw materials, particularly metals, are very important for sustainable functioning, since they are essential for the high-tech products such as electrical and electronic devices, photovoltaic systems, batteries, catalysts, optical fiber cables, synthetic fuels, _etc_. European industry needs sufficient access to certain mineral raw materials for the sound functioning of the EU's economy. However, the European Union (EU) is highly dependent on imports from third countries of strategically important metals, which are considered to be critical because of their economic value, the high supply risks affected by market distortions and the continuously decrease of their availability. An expert group under the auspices of the European Commission published in 2010, a list of 14 metal raw materials which are considered to be \"critical\" for the future sustainable development of EU: antimony, beryllium, cobalt, fluorine, gallium, germanium, graphite, indium, magnesium, niobium, platinum group metals, rare earths, tantalum and tungsten [1]. Due to their low concentrations in earth's crust, the critical metals are produced as by-products of other metals which are mined. During the last years issues concerning the EU policy on securing raw material supplies by improving resource efficiency and recycling, have been high on the political agenda. In November 2008 the new European policy entitled: \"The Initiative for raw materials to meet critical needs for growth and employment in Europe\" was adopted and promulgated by the EU [2]. This initiative refers to the need of the EU to follow a comprehensive policy for ensuring access to mineral raw materials in order to enhance competitiveness and to achieve the Lisbon partnership for growth and employment. The EU has many ore mineral deposits, even if their exploration and extraction are facing increased competition for different land uses and a highly protected environment, as well as several limitations in access to these deposits. Greece is one of the most significant metallogenic provinces of EU hosting a large number of ore deposits, which may provide an essential mineral wealth, including critical metals. Mining has been part of the Greek civilization since prehistoric times, when Greeks began extracting non-metallic minerals and metals for use. Ancient underground mines and ruins of metallurgical furnaces throughout Greece are witnesses of the intense exploitation of the metallic mineral resources, mainly gold, silver, copper, lead and iron. Especially during the Classical and Hellenistic times, famous mining centers operated in Lavrion (Attica), Sifnos and Milos Islands (Aegean sea), Pangeon Mt, Palea Kavala, Chalkidiki and Thasos Island (northern Greece) (Figure 1). In the last 70 years significant mining operations in Greece have focused on nickel, aluminum, chromium and iron-manganese deposits, as well as lead-zinc-(\(\pm\)Cu, \(\pm\)Au, \(\pm\)Ag) sulfide occurrences. However, several of these operations have been stopped in the last years due to various reasons. Recent investigations, especially in northern Greece (Macedonia and western Thrace), have revealed new prospects of gold-silver, copper, molybdenum-rhenium, antimony, tungsten and tellurium ore mineralization. According to [3] the total value of the indicated metallic mineral reserves of Greece exceeds \(\ell 72\) billion. It should be mentioned that Greece is the only country in the EU with large deposits of manganese, chromite, aluminum and nickel. It is the leading producing country in the EU for aluminum (from bauxite) and nickel (from laterite). Significant production of magnesium (from magnesite) is also reported. Greece has a comparative advantage in relation to other European countries due to the presence of a significant mineral wealth. In the last decades, the metal mining industry of Greece operated far below its productive capacity, with an exception of bauxite and laterite.