Granite

Buildings are built for a purpose: schools for education, offices for work, theatres for culture. Each building is a blend of form and function - to be aesthetically pleasing as well as to fulfill the purpose for which it was created. Foundations do not typically contribute to the architectural aesthetics of a building. Yet, without suitable foundations, a building will not function effectively, will be unsafe and its architectural merits will rapidly fade. Foundations must be designed to ensure that, under a wide range of defined loading conditions, movements of the supported structures are kept within acceptable bounds. Foundations are also required to ensure the robustness and safety of the structure in earthquakes, or due to ground collapse brought about by geological or man-made features and seasonal or tree-induced ground movements. Materiality in architecture is the concept of, or applied use of various materials or substances in the medium of building. Material is a relative term in architectural design and so may be used to designate materials which are considered to be virtual, (such as photographs, images or text) or other materials which are natural. Materiality in architecture is not limited to theoretical positions on the perceived materiality of images, texts, or other objects of representation. It may refer to the materiality of specific projects, where one would need to consider the full range of materials used. Building material is any material which is used for a construction purpose. Many naturally occurring substances, such as clay, sand, wood and rocks, even twigs and leaves have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacture of building materials is an established industry in many countries and the use of these materials is typically segmented into specific speciality trades, such as carpentry, plumbing, roofing and insulation work. One of the oldest construction materials is rock. From time in memorial rock has been used for residential and public buildings. It has been in constant use by the in people in the Stone Age, till the e-generation of today, and would be in use for its versatile nature, be it in construction field, decoration, statues, etc. Rocks have had a huge impact on the cultural and technological advancement of the human race. Rocks have been used by Homo sapiens and other hominids for more than 2 million years. Lithic technology marks some of the oldest and continuously used technologies. The mining of rocks for their metal ore content has been one of the most important factors of human advancement. In Geology, rock is a naturally occurring aggregate of minerals and/or mineraloids. The Earth’s outer solid layer, the ‘lithosphere’, is made up of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic. Rocks are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into igneous, sedimentary and metamorphic. They are further classified according to particle size. Igneous rocks are rocks which have crystallized from a melt or magma. The melt is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. The melt is hot and so passes upward through cooler country rock. As it moves it cools and various rock types will form through a process known as fractional crystallization. Igneous rocks can be seen at mid ocean ridges, areas of island arc volcanism or in intra-plate hotspots. The most common form of igneous rocks is Granite, which is easily available in the market. OCCURRENCE of Granite Granite is currently known only on Earth where it forms a major part of continental crust. Granite often occurs as relatively small, less than 100 km² stock masses (stocks) and in batholiths that are often associated with organic mountain ranges. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions. In some locations very coarse-grained pegmatite masses occur with granite. Granite has been intruded into the crust of the Earth during all geologic periods, although much of it is of Precambrian age. Granitic rock is widely distributed throughout the continental crust of the Earth and is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Despite being fairly common throughout the world, the areas with the most commercial granite quarries are located in Finland, Norway and Sweden (Bohuslän), northern Portugal in Chaves and Vila Pouca de Aguiar, Spain (mostly Galicia and Extremadura), Brazil, India and several countries in southern Africa, namely Angola, Namibia, Zimbabwe and South Africa. COMPOSITION Granite is primarily composed of potassium feldspar, sodium feldspar and quartz(10-50%). These minerals make up more than 80% of the rock. The various other minerals in varying percentage, which are constituted in it are stated as follows: Silica(SiO2) 70-77%
Alumina(Al2O3) 11- 14%
Potassium Oxide(P2O5) 3 – 5%
Soda(Na2O) 3 – 5%
Lime 1%
Iron(Fe2O3) 1-2%
Iron(FeO) 1 – 3% 
Magnesia(Mg0) 0.5 – 1%
Titina Less than 1%(.38%)
Water(H2O) 0.03%
 ORIGIN Granite is an igneous rock and is formed from magma. Granitic magma has many potential origins but it must intrude other rocks. Most granite intrusions are emplaced at depth within the crust, usually greater than 1.5 kilometres and up to 50 km depth within thick continental crust. The origin of granite is contentious. There are two theories for the origin of granite. • The magmatic theory states that granite is derived by the crystal fractionation of magma. Thus granite bodies are the result of intrusion of liquid magma into the existing rocks. • The granitization theory states that granite is formed in place by extreme metamorphism. There is evidence to support both theories, and both are useful to explain different observed features. The two may actually merge: as metamorphic conditions increase to the melting point of the metamorphosed granite, it will melt and become a liquid magma. Geochemical Origins Granitoids are a ubiquitous component of the crust. They have crystallized from magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. Fractional crystallization serves to reduce a melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon - alkali feldspar (rich in potassium) and quartz (SiO2), are two of the defining constituents of granite. This process operates regardless of the origin of the parental magma to the granite, and regardless of its chemistry. However, the composition and origin of the magma which differentiates into granite, leaves certain geochemical and mineralogical evidence as to what the granite's parental rock was. The final mineralogy, texture and chemical composition of a granite is often distinctive as to its origin. For instance, a granite which is formed from melted sediments may have more alkali feldspar, whereas a granite derived from melted basalt may be richer in plagioclase feldspar. It is on this basis that the modern "alphabet" classification schemes are based. Granitization An old, and largely discounted theory, granitization states that granite is formed in place by extreme metasomatism by fluids bringing in elements e.g. potassium and removing others e.g. calcium to transform the metamorphic rock into a granite. This was supposed to occur across a migrating front. The production of granite by metamorphic heat is difficult, but is observed to occur in certain amphibolites and granulites terrains. In-situ granitisation or melting by metamorphism is difficult to recognize except where leucosome and melanosome textures are present in gneisses. Once a metamorphic rock is melted it is no longer a metamorphic rock and is magma, so these rocks are seen as a transitional between the two, but are not technically granite as they do not actually intrude into other rocks. In all cases, melting of solid rock requires high temperature, and also water or other volatiles which act as a catalyst by lowering the solidus temperature of the rock.