other names: /
mineral class: Silicates
chemical formula: ?
Chemical elements: Silicon, oxygen, aluminum, iron, calcium, magnesium, potassium, sodium
Similar minerals: Gabbro
colour: grey black
crystal structure: /
mass density: about 2.5
Mohs hardness: about 5 - 6
stroke color: ?
use: Building material
General information about the basalt:
Of the basalt describes a rock that originated in the Tertiary, ie, up to seventy million years ago, by volcanic activity in subterranean lakes and streams formed by lava, and is detected on Earth as well as on the Moon, Mercury, Mars, and Venus. It develops due to tufa, which was thrown to the earth's surface in the course of volcanic eruptions and accumulated in huge layers. The resulting funnels filled with glowing magma, which developed into basalt at the edge of the funnels. In the process, such rock deposits were formed either as, on average, often hexagonal columns, as plates, prisms, spheres or aeration.
Depending on the chemical composition and coloring, a distinction is made between several varieties of basalt, such as dolerite, tachylite, basanite or Prikrit basalt. The most common form of basalt has a dark gray to almost black appearing dark blue hue, which is due to the silicates contained therein. Also reddish and brownish rock types, which are counted to the group of basalts, are widespread.
The name Basalt goes back to the people of Ancient Egypt, who mined such rocks in Ethiopia and gave them the name "basaltes". This name was probably adopted by Pliny and later found use in the Middle Ages. In particular, the German mineralogist and physician Georg Bauer, better known as Agricola, born in 1494, is said to be responsible for the dissemination of this name, which is still in use today.
Occurrence and localities:
Basalts occur in both oceanic and continental regions and describe the most widespread volcanic rocks. Almost all volcanoes worldwide consist of a predominant proportion of basalt, which in some countries covers an area of hundreds of thousands of square kilometers. The most important basalt fields are located in the northwestern United States, especially in Oregon and Washington, as well as in the South American Paraná basin and in much of India. On the Moon, mainly basalt lava fields such as the Mare Imbrium were found, occupying an area of over two hundred thousand square kilometers. Germany, Austria, Hungary, Slovenia, the Czech Republic and Romania, Italy, Sweden, Vietnam, West Africa, the USA and Mauritius are among the most important countries in which basalt is mined on a large scale.
Properties and Use:
Basalt is characterized by an enormous compressive strength and its high weight and was mined and processed by humans already in the Neolithic Age, since it hardly weathered and can therefore be very heavily used. Archaeological finds prove that basalts were used five thousand years ago as rubbing stones for painting grain. A systematic degradation of basalt is known only from Roman times, as the people made from this rock mills as well as private buildings, temples and streets. With the fall of the Roman Empire, the basalt was temporarily forgotten as a durable building material until in the 10th century began an intensive construction of castles and fortifications, which led to a new heyday of basalt mining. By the middle of the 20th century, many bridges, tunnels, stations. Built of churches, public buildings and viaducts made of this weather-resistant and durable material with a typical dark gray appearance that is characteristic of the appearance of the rock.