Bergarter

Bergarter, or rock types, are natural solid aggregates composed of minerals. In geology they are typically divided into three broad groups: igneous, sedimentary, and metamorphic. These groups reflect the processes by which the rocks formed and the conditions under which they were altered over time.

Igneous rocks form from the cooling and solidification of molten material. Plutonic or intrusive igneous rocks crystallize below the surface, producing coarse textures such as granite and diorite. Volcanic or extrusive rocks erupt or extrude at the surface and cool rapidly, yielding glassy or fine textures such as basalt, rhyolite, and obsidian. The mineral composition of igneous rocks is commonly described as felsic, intermediate, mafic, or ultramafic, with felsic rocks rich in silica and light-colored minerals like quartz and feldspar.

Sedimentary rocks accumulate from fragments of preexisting rocks or from minerals precipitated from water. They are classified as clastic (sandstone, shale, conglomerate), chemical (rock salt, gypsum, travertine), or organic/biochemical (coal, limestone). Sedimentary rocks often preserve fossils and show features such as bedding and stratification.

Metamorphic rocks arise from alteration of existing rocks due to heat, pressure, and chemically active fluids, without melting. They are grouped as foliated (slate, phyllite, schist, gneiss) and non-foliated (marble, quartzite, hornfels). Metamorphism can occur during mountain-building events or deep burial.

The rock cycle explains how bergarter can transform from one type to another through weathering, erosion, lithification, burial, metamorphism, and melting, linking the three main groups in a dynamic Earth system.