Indian Premium Black Granite is produced from the same quarry as our Absolute Black Granite and our Classic Black Granite. The difference in shade is that Premium Black Granite is quarried at different face levels in different pits, all within the same very large quarry, quite simply the deeper in the pit we quarry, the darker the shade. The Premium Black Granite is quarried at the lowest levels and therefore much more difficult to extract, the lower the level in the pit the more difficult it is to extract owing to the lack of work space.
The Premium Black Granites quarried in the lower levels are always in extremely high demand therefore command a premium price, hence the quality name!
Indian Premium Black Granite is a Dolerite, a fine to medium-grained black basalt. This stone internationally may be nominated as a granite however in the area of application of the European Standard (EN) this stone must be nominated as dolerite.
Prospective users of "Black Granite" requiring a complete petrographical test should contact one of the following which all open in a new window:
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ASTM
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BRE
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Sandberg
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Stats
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UKAS
The Underneath Information Is Given In Good Faith For Informational Purposes Only.
Description: Dolerite (Diabase, Microgabbro): A dark-coloured, medium-grained igneous rock which contains plagioclase feldspar of labradorite composition and pyroxene of augite or titanaugite composition as essential minerals, and magnetite, titano-magnetite, or ilmenite as accessory minerals. Where olivine also occurs as an additional mineral, the rock is termed an ‘olivine dolerite’. Where quartz occurs as an additional mineral in the groundmass, the rock is termed a ‘quartz dolerite’. Dolerites are the medium-grained equivalents of basalts and, like the basalts, can be divided into alkali and tholeiitic types. Dolerites are commonly found in shallow level intrusions such as dykes, sills, or plugs.
Description: Diabase - also called Dolerite: A fine to medium-grained, dark gray to black intrusive igneous rock. It is extremely hard and tough and is commonly quarried for crushed stone, under the name of trap. It makes an excellent monumental stone and is one of the dark-coloured rocks commercially known as black granite. Diabase is widespread and occurs in dikes (tabular bodies inserted in fissures), sills (tabular bodies inserted while molten between other rocks), and other relatively small, shallow bodies. Chemically and mineralogically, diabase closely resembles the volcanic rock basalt, but it is somewhat coarser and contains glass. With increase in grain size, diabase may pass into gabbro.
About one-third to two-thirds of the rock is calcium-rich plagioclase feldspar; the remainder is mostly pyroxene or hornblende. In diabase, poorly formed pyroxene crystals wrap around or mold against long, rectangular plagioclase crystals to give it the characteristic texture known as diabasic or ophitic. The larger pyroxene grains may completely enclose plagioclase; but as the quantity of the latter increases, pyroxene appears more interstitial.
Diabase may show varying degrees of alteration: plagioclase is converted to sassurite; pyroxene to hornblende, actinolite, or chlorite; and olivine to serpentine and magnetite. In British usage, such altered rock is called diabase. Some diabase masses have been subdivided by systematic fractures into rectangular blocks. Subsequent alteration and weathering along these fractures have disintegrated and rounded off block corners and edges (spheroidal weathering), leaving regularly spaced, spherelike masses of fresh diabase enveloped by shells of progressively more altered and disintegrated material.
Description: Gabbro: Any of several medium or coarse-grained rocks that consist primarily of plagioclase feldspar and pyroxene. Essentially, gabbro is the intrusive (plutonic) equivalent of basalt, but whereas basalt is often remarkably homogeneous in mineralogy and composition, gabbros are exceedingly variable. Gabbros are found widely on the Earth and on the Moon as well.
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