_Granites_ are rocks which have been formed by the union of three different minerals in a state of fusion; these, on cooling, have crystallized and become distinct from each other in the mass. It is on the varied proportions in which these three constituents are combined, that the colour, hardness, durability, and beauty of the various granites depend. The light-red and rose-coloured granites contain the felspar in greatest abundance and in the largest crystals; but this mineral varies in hue from the purest white to nearly black; it is the ingredient most acted on by the atmosphere; the rock, therefore, which abounds in it, though it may be more beautiful to the eye, and more easily worked at first, is not so durable as that which contains it in smaller crystals, and with a larger proportion of _quartz_. It is to this last-named mineral that granite owes the sparkling appearance which it presents when the sun shines on it; quartz is the hardest and most imperishable of the three minerals which form the granite-rock. The third, _mica_, is distinguishable from the other two by its satiny, shining, dark hue, and is very apparent in the coarse-grained, handsome stone of our own country, brought from Cornwall. When the felspar is replaced by another mineral called _hornblende_, the stone is of a dark-greenish hue, and the component parts are in a finer form and less distinguishable from each other. The Aberdeen granite is an example of this kind, which is more durable than the former, though not so pleasing to the eye. Granite occurs in all the larger mountain-ranges, and in isolated masses in every country; not being a stratified rock, and being excessively hard, it is difficult to quarry and get out in manageable masses. Blasting with gunpowder is the mode usually employed in this country; the pieces detached by this means are hewn roughly into form on the spot by a small pickaxe. Aberdeen granite is quarried by cutting a deep line some yards long, and placing strong iron wedges at equal distances in this line; these wedges are struck in succession by heavy hammers till the mass splits down. This, or analogous modes, may always be employed when the rock approaches a slaty or stratified structure, as is the case with some nearly related to granite. Another method of detaching masses of rock, is by driving wooden wedges into a deep fissure, either natural or artificial; the wedges are then wetted, and the consequent expansion of the wood bursts the rock asunder. As granite has always to be brought from a great distance to the spot where it is wanted, because its natural localities are far from the places where edifices are usually constructed, and also on account of its hardness, this rock is only used for important buildings, such as bridges, markets, churches, &c., and not commonly even for these. London and Waterloo bridges, Covent Garden and Hungerford markets, and the York column in Pall Mall, are instances of its use in London.