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Granite

layers, composed and usually

GRANITE, CorSirlia, orhirithi•.—This beautiful rock (which probably biliong,s to the sienite formation) was discovered by Barrel. in the island from which it derives its name. its composition is very ext ; it has a basis of gray granite, which, however. in most parts exhibits a con siderable portion of hornh'ende. But what more particularly characterizes it, is a number of balls, of from one to two inches in diameter, each composed If several concentric and perfectly parallel layers. the outermost of which, generally white, opaque, and two or three lines thick, is composed of (waltz and feldspar, blended ill various proportions, and exhibiting a radiated appearance, rather converging ti(wa•ds the centre of the ball. The second layer, which is of a greenish black colonr, and about one line thick, is composed of fine laminarhiIruillcude ; and this is succeeded hy 0 white and usually transhleid quartz layer, of about four or five lines in thickness, inclusive of two or three very thin lay ers of hornblende, that are seen within the substance of this third principal layer. Each of these layers is generally

of equal thickness in the MO de of its circumference. These three parts may he considered as the coating : the interior each ball is less defined than the surrounding layers. and consists of a blackish and a whitish substance. the former surrounded by, and pacing into the latter, the centre of which is usually a dark gray spit.

The quarry of this rock is unknown, a single block only having been found in the gulf of Valinco, in Corsica : its weight was about 8011)., hill it •a-; soon broken into small fragments, hich are now distributed a collectors. There is a beautiful vase Of it, one toot six inches high. in the cabinet De(Wie. The granite of Corsica is figured by Fatijas de St. Fond. in his Essai de Gt•olo!pe, and in 7AI r. Sowerby's /;frolic iner«logg.

Ainimg the red granites, we have ivhat is called red oriental granite, which usually contains hornblende, often in large separate patches.