Granite

What is written on the plate:

Granite

Granites are magmatic rocks, which are formed during the solidification of a silicate melt during slow cooling. Biotite, muscovite, feldspars (plagioclase and potassium feldspar) and quartz crystallize successively. This granite intruded as SiO2-rich melts into Lower Carboniferous graywackes and became stuck at depths of about five to ten km.
Later uplift brought it to the earth's surface.

Henneberg-Granit, Ober-Karbon, Heberndorf, Thüringisches Schiefergebirge, ca. 320 Ma

Granite

Location: Heberndorf, Thuringian Slate Mountains

Age: ca. 320 million years

Heberndorf

Image: Google Maps

Granite is a massive rock with coarse crystals that belongs to the group of deep igneous rocks (plutonites). It is rich in quartz and feldspars and also contains dark minerals such as mica. The name "granite" is derived from the Latin word "granum", which means "grain" and refers to the granular appearance of the rock

Granite is often used as a generic term for various plutonic rocks that have similar characteristics to granite. These include granodiorite, tonalite, monzonite, diorite, and anorthosite. These rocks are petrographically referred to as granitoids or granitic rocks and have a quartz content greater than 20 percent. It is important to note that dark natural rocks of igneous origin, often referred to as "black granites," are not granites proper, but are usually gabbros, norites, microgabbros, basalts, and basanites [1External link].

The composition of granite consists mainly of three minerals: feldspar, quartz, and mica. The content of these minerals can vary, resulting in different colors and textural variations of granite. The overall light color of the rock is due to the dominant orthoclase feldspars, while dark mica such as biotite and light mica such as muscovite also occur. Quartz is another important mineral in granite. The exact coloration of granite can range from pink, white-gray, greenish, yellowish, dark gray to blue-white [2External link].

Granite usually occurs in massive form and may be dissected into cuboidal blocks by fissures. These fissures may be horizontal and vertical, forming a three-dimensional network of fissures in the rock. However, it is also possible that granite is platy in the roof of the intrusion [1External link].

Gneiss, on the other hand, is a metamorphic rock with a parallel texture that contains more than 20 percent feldspar. It is formed by the metamorphism of rock under high pressure and temperature. Unlike granite, gneiss has a tilted texture (foliation) and has a higher load-bearing capacity due to its aligned mineral grains. Gneisses are distributed worldwide and are commonly found in the ancient cores of continents and in crystalline zones of younger folded mountains [3External link].

Location of the rock granite near the village Heberndorf

Image: Thomas Voigt