A slab is a smooth, flat rock , of thin thickness. These stones are usually used in paving and roofing .
Limestone , shale and sandstone slabs are among the most used. Many times the use of one or another slab depends on the availability that exists at the regional level. The use of limestone or schist slab to make residential roofs is especially common in mountain areas.
Schist is understood to be a group of rocks that is characterized by the predominance of lamellar minerals , which improve their fragmentation into thin layers. Metamorphic rocks , on the other hand, are metamorphic rocks, that is, they are formed by the modification of others through the process known as metamorphism .
Another related concept is limestone , a sedimentary rock that is mainly composed of calcium carbonate, although it is common for it to have traces of other carbonates, such as magnesite. Limestone can also have in its composition a certain percentage of minerals such as hermatite, clay, quartz and siderite, which can modify its degree of coherence and color.
Micaceous sandstone tiles usually come from quarries or natural stones. Its thickness is greater than that of slate, a rock that is also metamorphic, although homogeneous, with a fine grain, which is formed by the compaction of shales by low-grade metamorphism. Its color is generally dark blue and its material is opaque. It usually has a structure of flat leaves or slabs. One of its disadvantages is that it has a considerable weight, so the structure on which it rests must be very rigid.
A name some experts give to micaceous sandstone tile is phonolith . This is due to the sound it makes when struck, which is similar to that of a bell. The word phonolith is made up of two parts: the prefix fono- , whose origin goes back to the Greek language and denotes the concepts of "sound" or "voice", and the suffix -lito , which also comes from Greek and means "stone." ».
An example of the use of flagstones can be found in the so-called black architecture . In this case, slate slabs are used in homes , livestock or agricultural structures and even in road infrastructure such as bridges and roads.
Black architecture based on slate slabs is very common in certain Spanish regions. This is due to the abundance of slate in the area , which helped define the architectural style of the place.
Some of the slabs come from volcanic areas, and these are part of the group known as andesites precisely because they are one of those that stand out in the Andes Mountains . Thanks to the presence of some minerals, such as iron and manganese oxide, in certain rocks you can see a reddish, greenish or bluish hue on a base that is usually gray.
Laja is also the name that identifies a commune in Chile and a municipality in Bolivia . In the Chilean case, it is a city that is part of the province of Biobío . It has more than 22,000 inhabitants and has several lagoons among its main tourist attractions.
In Bolivian territory, meanwhile, Laja is a town in the province of Los Andes , in the department of La Paz . It is located at a distance of 35 kilometers from the city of La Paz , at 3860 meters of altitude . About 24,000 people live in Laja .
Lajas (plural), finally, is a municipality in Puerto Rico (which is known as “the town of the big-headed pineapple” ) and another in Cuba (whose full name is Santa Isabel de las Lajas ).