Granite is a plutonic rock made up essentially by quartz, feldspar and, normally, mica. It is the most abundant rock in the continental crust. By slowly solidifying at very high pressure, magma is produced with a high content of silica, the result of the fusion of the rocks formed by the continents, subjected to the heat of the mantle in their lower sections.
As this magma contains less magnesium than the continental crust, it has less specific weight and therefore it rises through the latter in characteristic structures in the shape of inverted drops which usually solidify before reaching the surface. For the rock to be formed to be granite it is necessary for it to slowly solidify at great pressure. The size of the feldspars is an indication of the speed of solidification and, the larger they are, the lower it is. These solidified structures appear on the surface due to the action of the erosion and are called batolites. On account of their great hardness, it is common for them to end up being the top of mountains which are distinguished by their typical rounded shape.
There exist 8 varieties of Black Granite:
- Negro Batalla Granite of average grain extracted from the pluton of Valencia del Ventoso. Mining and average reserves. All kinds of uses.
- Negro Extremadura Granite of thin grain and dark color, extracted in Burguillos’s pluton. Good mining and reserves. All kinds of uses.
- Negro Fantasía Granite extracted in Quintana de la Serena. All kinds of uses. Good access. Moderate mining.
- Negro Fino Granite of thin grain extracted in Barcarrota’s pluton. Good access. All kinds of uses. Good mining and big reserves.
- Negro Grapesa
Granite of thin grain extracted in the batolito of Central Extremadura. Good mining. All kinds of uses.
- Negro Ochavo Black granite of thin grain, extracted in Burguillos’s batolito. Medium mining. All kinds of uses.
- Negro Ochavo Especial Black granite of thin grain, extracted in the batolito of Valencia del Ventoso and of Burguillos’s batolito. Medium mining. All kinds of uses.
- Negro Villar Black granite of thin grain corresponding to a dike of diabasa. Medium mining. All kinds of uses.