Permits for exploration and mining rights for exploitation of mineral resources may be granted to nationals and incorporated companies of the Member States of the EU, the EEA and the Swiss Confederation and the Member States of the OECD. Third-country parties may be granted an exploration permit or mining rights only subject to reciprocity.
"Article 1 (subject to law a)
(1) This Act determines the conditions for the search, exploration and exploitation of mineral resources, regardless of whether they are in the soil, on its surface or in waters, the conditions for abandoning their exploitation and the conditions for ensuring protection and health in the performance of works regarding the exploration, exploitation and non-exploitation of mineral resources and regulates inspections.
(2) The provisions of this Act shall not apply to:
1. exploration and exploitation of sand, gravel and gravel from water and coastal lands; and
2. elimination of the consequences of natural and other disasters in areas where mines are closed in the manner and under the conditions determined by this Act .
(3) Notwithstanding the provisions of the first and second paragraphs of this Article, the prospecting, exploration and exploitation of oil and natural gas at sea shall be prohibited.
[...]
Article 2 (meaning of terms)
In this law , the terms used have the following meaning: [...]
2. Mineral resources, other than geothermal energy sources, are non-renewable natural resources that are directly or indirectly economically exploitable.
2.1. Mineral resources are all organic and inorganic natural raw materials that are found in solid, liquid or gaseous state in natural deposits, solutions, sediments or tailings.
2.2. A geothermal energy source is heat energy that is located in geological layers below the earth’s surface and is renewed by heat flow from the Earth’s interior.
[...]
Article 6 (conditions for obtaining a exploration permit and mining rights for exploitation)
(1) A permit for exploration and a mining right for exploitation may, in the manner and under the conditions determined by this Act, be obtained by a legal or natural person:
-  who is established in the Member States of the European Union, the European Economic Area and the Swiss Confederation and in the Member States of the Organization for Economic Co-operation and Development (hereinafter referred to as "the Contracting States") or is a national of a Contracting State, and
- who is not from a Contracting State but from a third country, but only if the condition of material reciprocity is fulfilled. This condition is considered to be fulfilled if the interested party, which is from a third country, has its registered office or residence in the Republic of Slovenia and can perform activity in its own country under the same or similar conditions under which it can perform activity in the Republic of Slovenia. In the case of the registered office of a legal person or the residence of a natural person in several third countries, the rule of law of the country which is the strictest shall be taken into account in determining reciprocity. [...]" (Mining Act (Official Gazette of the Republic of Slovenia, No. 14/14), last amended on 2 November 2017, Articles 1, 2 and 6 [google translation])
Mining Act (Official Gazette of the Republic of Slovenia, No. 14/14), last amended on 2 November 2017, Articles 1, 2 and 6
[<a href="http://www.pisrs.si/Pis.web/pregledPredpisa?id=ZAKO5706">Act</a>]