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GRANITE

ORIGINS

The granite is a plutonic igneous rock formed by the slow cooling of a magma (melted aluminium) to big depths of the terrestrial bark.
This prolonged cooling allows that they form big glasses, giving place to the crystalline texture characteristic of the granites.

COMPOSITION
The granitic rocks are constituted by three essential minerals: quartz, feldspar and micas; in addition to a very variable group of mineral accessories, that present  in inferior percentages to the 5 %, as they can be the apatite, esfena, oxides, allanita, circón, anfíboles, etc.

So much the process of training million years ago like the own chemical composition of the granites, does of these stones some exceptional materials for the construction from the aesthetic point, but especially, from the technical point with high values of resistance and durability.

Commercially they designate  “Granites” To a group of crystalline rocks that include feldspars in his composition and whose glasses are used to to differentiate to simple sight. Like this, inside this term  encompass plutonic igneous rocks (granite in strict sense, granodiorite, sienita, diorite, gabro..), some volcanic igneous rocks (basalt or andesite) and metamorphic rocks (gneis, migmatite, milonita).

CHARACTERISTICS
Physical characteristics


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Bulk density:

The bulk density of granites is varies considerably depending on the type considered. Usually values of over 2.6 t/m3 are reached, the so-called black granites having the highest density. These values in themselves indicate that it is a building material with outstanding features.

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Water absorption at atmospheric pressure:

Water absorption in granites is quite low, normally with values of below 0.6%, which generally implies good frost resistance and low maintenance cost.

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Frost resistance:

In keeping with their physical characteristics, granites usually have outstanding frost resistance, even in areas with extreme weather conditions.

Mechanical characteristics

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Compressive strength:

Granites have a very high resistance to compressive stress, with much higher values than those of concrete.

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Flexural strength:

The degree of flexural resistance of granite means that today it is possible to make thin pieces for applications as diverse as flooring, cladding panels, lintels, etc.

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Impact resistance

The impact resistance of granites is quite high, making them very suitable for use in flooring or skirting boards, where the risk of impacts is higher.

Construction characteristics


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Wear resistance:

Wear resistance is the capacity not to lose mass due to friction. Compared with other ornamental rocks, granite has a high degree of wear resistance due to its quartz content.


Huella dejada en las probetas después de un ensayo de abrasión

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Workability:

Workability is the capacity of a rock to adopt the desired shape, size and surface finish. Granite, due to the homogeneity of its crystalline structure, can adopt any shape and a wide range of sizes.

QUARRYING

Traditionally, granite is extracted from quarries by diamond wire sawing, ranging shearers and circular saws. This involves the creation of successive descending banks called tiers.

The quality control of granite starts at the quarry.
On average, 25% of the granite quarried is marketed in block form. Pieces with any impurities are set aside for a second quality test. Any blocks that are slightly fractured are split to obtain breeze blocks, curbs or paving slabs.

Cluster del Granito © 2012 |  Centro Tecnológico del Granito Ribeira, S/N, Torneiros. 36410 | O Porriño (Pontevedra)

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