Origins of architectural heritage: the resources and variety of natural stones in Slovenia

The distinct geological variation of Slovene’s territory, which includes all three major types of natural stone (sedimentary, igneous and metamorphic), offers an ample selection of building and art materials to be chosen based on their properties and/or aesthetic appearance. The tectonic diversity of the area caused some difficulties in extracting some of the natural stones, resulting in quarries being abandoned for economic and spatial reasons, but some beautiful examples of the use of lasting value in both construction and art still persist. Examples include the abandoned quarries of Pohorje marble and Podpeč limestone, where extraction has been documented from as early as the Roman times, with the latter also designated as a Global Heritage Stone Resource. The Pohorje mountains are an area of granodiorite as well as green cizlakite, the latter being Slovenian endemic. Furthermore, the Kras (Karst) region is one of the most interesting areas containing natural stone reserves in Slovenia, with a large variety of Cretaceous shallow-water limestones. All of these are abandoned, with the two natural stone quarries still operating being associated with the presence of rudist biostromes and bioherms, which are responsible for the aesthetic appearance of these natural stones. It is also characteristic of Slovenia to use a variety of local rocks, such as sandstone, conglomerate, breccia, shale and tuff, to give character to vernacular architecture. Some of the quarries are designated and protected as valuable natural features or natural monument, while several buildings decorated with Slovene natural stones are declared as cultural monuments of local or national importance or included in the UNESCO World Heritage List. This paper presents the most significant Slovene quarries of natural stones that have been used in architectural heritage, the mineralogical and physical-mechanical characteristics of these stones, as well as examples of their use in monuments.