Geology is one of the fundamental sciences. Its subject are solid, liquid and gaseous substances that make up our planet. It studies the composition, structure, physical and chemical properties of the Earth and its various parts, as they constantly evolve, move and change.
Geology is also useful in everyday life. As geologists discover, investigate, explain and predict future movement of metallic and non-metallic mineral deposits, as well as fossilised solid and liquid energy sources, they can predict certain natural processes that threaten man, his possessions and the environment – in other words, they are able to predict what is known as geohazards. Most notably, based on geological knowledge, we are able to design buildings that are safe from earthquakes.
Growing geological knowledge and deeper understanding of paleoclimatic and other past changes of the environment enables us to better predict climate changes and geological events, such as landslides, earthquakes or tsunamis. These factors are becoming paramount to human survival on this planet.
Although the object of geological research is mostly inanimate nature, in the past centuries the origin and evolution of life had been proven through fossils, which also fall within the framework of geology.
The surface of our planet is being created by forces originating from the depths of the Earth and the power of the Sun, gravity and water. The diversity of geological environments, i.e. geodiversity, in turn provides the basis for biodiversity.
Geology is therefore the science of our environment, of our planet – a seemingly large, albeit very sensitive and temporary shelter that drifts through space with no propulsion of its own, but is guided only by the gravity of the Sun.
In general, minerals have a crystalline structure. Therefore, minerals are also crystals. A crystal is a solid substance whose atoms or molecules are arranged symmetrically, which results in symmetry of the external form. When minerals are bound by more or less flat surfaces that can be admired with the naked eye, we speak of crystals. There are, of course, exceptions to this rule, that is, there exist minerals that do not have a crystal structure. They are called amorphous minerals. Notable examples include opal and obsidian, a type of volcanic glass, as well as mineraloids such as copal and amber. Up to today, more than 4,000 different naturally occurring minerals have been identified. Each of them has a unique crystal structure which is determined by the arrangement of elements in the crystal lattice and by their chemical composition.
Crystals are formed in natural environments through crystallisation processes. The vast majority of these processes are hidden from view, occurring deep below the Earth’s surface, or are very slow. This makes them difficult to study. Crystallisation in solutions or melts begins with the formation of crystallisation seeds or crystallization nuclei. Once a nucleus forms, the crystal begins to grow around it in such a way that the elements of the basic cell of the crystal are repeated in all three directions of space. Formation of a crystal depends on several factors, such as the presence of chemical elements, appropriate temperature and pressure, space, time, as well as the pH and Eh of the environment. Depending on the chemical composition and crystal structure, minerals and the rocks they are made of display different properties.
Our ancestors soon realised that some minerals can be very beautiful. In Slovenia and across the world, many archaeological artifacts were found that bear witness to the fact that minerals and precious rocks have always been very popular, admired and valued as aesthetic objects. This is the precious world of gems. Even today, jewels are used as expressions of personal, emotional and sensual worth and are generally understood as symbols of wealth and power. Natural stone has always been the noblest, but also the most durable natural material, which has been confirmed again and again by archaeological finds. Many works of art also make use of natural stone. Gems were used for aesthetic purposes by artists and noble stones served as building material for countless craftsmen across time and space.
Earth is a living, dynamic planet. Unlike the Moon, our Earth is an ever-changing World. We can observe how some rocks are formed, for example during volcanic eruptions, or how they are destroyed by weathering and how they transform under erosion. The main drive for the circular flow of rocks on Earth is hidden deep inside our planet. If you were to cut through the Earth, you would see a layered structure composed of a core, a mantle and a crust. The core was formed very early after the birth of our planet, when heavier metallic, mainly iron-nickel minerals were separated from silicate minerals, which remain in the mantle and the crust.
Processes inside Earth and on its surface cause the continuous formation and reformation of rocks, which circulate in the so-called rock cycle. As the magma cools beneath the surface of the Earth, intrusive rocks are formed. Meanwhile, the surrounding rocks change into contact metamorphic rocks as a result of increased temperature. In a process that is called convection currents, magma from the Earth’s depths rises towards the surface through areas of rifting, which causes the continental crust to break up. Here, submarine springs of basaltic lava create new oceanic crust. Molten magma also flows to the surface through volcanic hotspots, which form the volcanoes of volcanic island chains, and through volcanoes above subduction zones, where oceanic plates subduct under continental plates. Along these subduction zones, upon the collision of two continental plates, high mountains are formed. By transportation, sedimentation and solidification of their weathered remains, clastic sedimentary rocks are formed. Sediments can also be produced as a result of chemical precipitation or by the excretion of marine organisms (coral reefs, etc.). In cases where tectonic plates collide and transport sedimentary rocks to lower layers of the Earth, they are transformed under the influence of increased pressure and temperature into metamorphic rocks. If they sink even deeper into the Earth’s interior, they melt again and form a new generation of igneous rocks. In rare cases, a special type of volcano can eject extrusive rocks mixed with diamonds to the Earth’s surface. Finally, space rocks are brought to Earth by meteorite falls.
Slovenia’s largest mercury deposit is in Idrija. It was discovered more than 500 years ago. Initially, prospectors simply dug holes in the ground and looked for drops of native elemental mercury. Soon the mineral ore of cinnabar was also discovered and from it, mercury was extracted on the spot in special mounds made of alternating layers of ore and wood.
Pyrite is one of the most common sulphide minerals. It is yellow or gold in colour and has a distinct metallic lustre. It is able to form over a very wide range of temperature and pressure, which means it can be found in igneous, sedimentary or metamorphic rocks.
Crystals and wine
Minerals are solid substances with characteristic chemical composition and internal structure. In nature, they are formed deep in Earth’s interior by precipitation from melt (e.g. diamonds), by crystallisation from hydrothermal solutions (e.g. quartz, claystones) or directly from gases near volcanoes (native sulphur).
Eclogite – a special gem from Pohorje
Eclogite is a very attractive, highly metamorphic rock mainly consisting of two minerals: the green-coloured omphacite and the deeply-red garnet. It can also contain other minerals in smaller, but still noteworthy quantities: kyanite, zoisite and corundum.
Ore treasures of Slovenia
Turbulent geological past resulted in high mineral variety on the territory of Slovenia. Minerals formed across a wide range of conditions: in sedimentary layers, through magmatic processes, in hydrothermal solutions, or simply in rock metamorphosis.
Calcite (CaCO3) is the most common mineral in Slovenia. It is the building block of various rocks such as limestone, marble, tufa, etc. It also forms unique stalactite formations inside caves. It can be admired in more or less perfect crystal form inside cavities and cracks within limestone or in septarian concretions.
Minerals of the Sitarjevec mine near Litija
The lead and zinc mine of Litija, popularly known as Sitarjevec, lies on one of Slovenia’s largest ore deposits. Litija itself is probably Slovenia’s oldest mining town. Mining operations here date back to the time of the Celts, who settled here to mine lead.
Mineral attractions of Slovenia
The Minerals of Slovenia collection covers all deposits that have been discovered in recent times. The majority of minerals are from the territory of Slovenia and were found in the 1990s and later. This was a time when some Slovenian prospectors found a renewed interest in home soil exploration.
Calcite from Peči pri Kropi na Gorenjskem
Calcite has the chemical formula CaCO3 (calcium carbonate) and is one of the most widespread minerals in Slovenia, being a major component of limestone, the most common Slovenian rock.
Remšnik mine: history – geology – minerals
There is an entry in the mining book A under number 2901, date 14 October 1850: Drauwald Mine (Drava Forest mine), owners Jakob Krušnik, Karl Kranz and Johan Baumgartner.