USEFUL MINERALS. 



building-stones anywhere found, but its compara- 

 tive hardness renders it costly to work. Binny 

 Quarry, near Linlithgow, has furnished the stone 

 for the finest buildings erected in Edinburgh of 

 late years. The flagstones from the Old Red 

 Sandstone of Forfarshire and Caithness, especially 

 the former, are largely employed for foot-pave- 

 ments. Some of the Yorkshire flagstones are 

 also extensively used for pavement and like pur- 

 poses. The millstone-grit of Northumberland 

 and adjoining counties furnishes grindstones. A 

 curious flexible sandstone is found not far from 

 Delhi, in India, examples of which may be seen 

 in most of our public museums. 



Sand. Sand, in the great majority of instances, 

 is composed of grains of quartz more or less pure ; 

 sometimes, however, it is formed of fragments of 

 shells, or coral, and more rarely of particles of 

 iron ore, and even of gems. As is the case with 

 clay, the most valuable kind of silicious sand is 

 that which is either white or will burn white. 

 This variety is highly prized for making the finer 

 kinds of glass, and is found at Alum Bay in the 

 Isle of Wight, and a few other localities. For 

 glass-making, it is first washed and calcined. 

 Some kinds of sand are specially adapted for mak- 

 ing the moulds used by founders for casting metal 

 objects. The commoner sorts are in request for 

 the making of mortar, in causewaying, in the 

 manufacture of coarse glass, and for many other 

 purposes. 



Granite. For reasons we have not space to 

 state, many geologists are now of opinion that 

 granite is, in some cases, a metamorphic rock, 

 although in others it must be regarded as a 

 truly igneous rock, which has invaded sedi- 

 mentary strata in a fluid or semi-fluid state. A 

 typical granite consists of quartz, felspar, and 

 mica ; and a typical gneiss, of the same three 

 minerals arranged differently namely, in irregu- 

 lar layers. Syenite is a granite where the mica 

 is replaced by hornblende. Some granites contain 

 additional minerals, such as schorl, while others 

 termed two-grained contain only quartz and fel- 

 spar. Granite is one of the most prevalent of 

 rocks all over the world, and forms the great bulk 

 of many mountain chains. 



Of English granites, those of Cornwall and 

 Devonshire are the best known, and they are 

 extensively used in London and other places in 

 the construction of bridges, embankments, and 

 architectural works. In one year forty thousand 

 tons, valued at ,75,000, have been shipped from 

 Cornwall. Granite is also obtained in West- 

 moreland and in Leicestershire. In Scotland, 

 this rock is largely quarried at Dalbeattie in 

 Kirkcudbrightshire, in the Ross of Mull, and in 

 Aberdeenshire. The beautiful red and blue gran- 

 ites found near Peterhead are now extensively 

 worked, by cutting and polishing machinery, in 

 Aberdeen, into columns, pedestals, fountains, 

 tombstones, and other objects. Many of these, 

 as well as much of the gray granite paving-stone 

 of Aberdeen, are sent to London. Some jewellery 

 is also made of Scotch granite. There is some 

 good granite found in Ireland ; indeed, the most 

 extensive range of it in the British Islands extends 

 S.S.W. of Dublin for seventy miles. The great 

 monolith called Pompey's Pillar, at Alexandria, 

 one hundred feet high, and ten feet in diameter, 

 is of red granite, and so also is the external casing 



of many of the Pyramids. The colour of granite,, 

 as well as its durability, depends chiefly on the 

 felspar. Some kinds of it are the most enduring ;. 

 some, again, as, for example, the decomposing: 

 granite of Cornwall, are among the most perish- 

 able of rocks. A striking example of its lasting 

 nature may be seen in the fagade of the Carlton, 

 Club in London, erected in 1847. Here the polish 

 on the columns of red Peterhead granite is quite 

 undimmed, while the limestone mouldings are fast 

 crumbling away. 



Serpentine Meerschaum Talc. These are- 

 magnesium silicates. Serpentine is a metamor- 

 phic rock, found in several localities in the 

 British Islands, but most largely worked in Corn- 

 wall. It is perhaps the most beautiful of all our 

 native ornamental stones. Its most prevalent 

 colour is dark green, but, like marble, which it 

 much resembles, it occurs of many colours and 

 of various patterns, indeed rarely without veins, 

 blotches, or mottling. Although comparatively 

 soft, it takes on a beautiful polish, and is much 

 more durable for external work than marble. Of" 

 late years it has been extensively used in Eng- 

 land, both externally and internally, for decorative 

 architecture. Meerschaum, resembling serpentine 

 in composition, is found in Asia Minor and a few- 

 other places. The name signifies 'foam of the 

 sea,' from its lightness and white colour. Its chief 

 use is in the manufacture of tobacco-pipes, large 

 numbers of which are made in Germany. Talc 

 is another hydrous silicate pretty generally dif- 

 fused. Steatite, or soapstone, is another mineral 

 of the same class, and agalmatolite, yet another,., 

 with potash and alumina instead of magnesia. 

 This last is much used by the Chinese for carving, 

 into grotesque figures. Steatite, being very refrac- 

 tory, is sawn into slabs for lining furnaces and. 

 stoves ; in Germany, it is made into gas-burners. 

 It is used to give translucency to porcelain, as a., 

 polishing material, and for several other purposes. 

 Potstone, or lapis ollaris, is an impure talc, made- 

 into culinary vessels in Lombardy. 



Mica Asbestos Jade Lapis Lazuli. These 

 are anhydrous silicates of various bases, but chiefly 

 of magnesia. Mica, one of the component parts 

 of granite, occurs of several varieties, but it is- 

 only when it is found in large thin transparent 

 plates that it is used in the arts. It is not easily 

 acted on by heat, and is consequently used for 

 lanterns and the doors of stoves. Asbestos is a 

 fibrous variety of hornblende, which can be woven 

 into an incombustible cloth. Fabrics made of it 

 were used by the ancients to wrap up the bodies 

 of the dead about to be burned. Jade, nephrite ; . 

 or axe-stone, is a beautiful, hard, translucent mine- 

 ral, found of several colours, but the best known 

 are leek-green and white. The finest white pieces 

 are said, and perhaps truly, to be valued by the 

 Chinese at more than their weight in gold. At 

 anyrate, some beautifully carved vases, cups, and 

 like objects brought from China, have sold of late - 

 years at very high prices in England. In New 

 Zealand and Western America, the green variety 

 is carved into images and fanciful objects, and 

 also, on account of its hardness, formed into axes. . 

 Lapis lazuli, or azure-stone, is a silicate of alumin- 

 ium, sodium, and calcium, with smaller quantities, 

 of other substances. It is of a rich azure-blue 

 colour, often mottled with gold-like spangles, and 

 has been long prized as an ornamental stone. It. 



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