I860.] JBEVI8 — KLOCBSB BOCKS OP TU8CA2TT. 481 



rocks; piercing the Upper Cretaceous beds; prevailing colour deep 

 olive- or leek-green, with metallic-looking grey or blackish crystals 

 of bronzite, generally not exceeding a quarter <>f an inch in length ; 

 extremely compact and difficult to cul ; susceptible of a fine polish 

 (whence its employment in architecture); never accompanied by on a. 



II. Ewpkotide or Qranitone. — Typical form a very dense rock, 

 with large crystals of diallage and milk-white or slightly Bteel-grey 

 crystals of felspar of tin* hardest kind. The latter are replaced in 

 some localities wholly or in part by steatite — as at Empruneta, where 

 the diallage is easily cleaved by the nail : this is fawn-coloured, and 

 when in large crystals, from its Boftness, renders the rock unfit for 

 building-purposes, the constituent parts having very unequal hard- 

 ness. In contact with the diallagic serpentine it produces a meta- 



morphism of thai ruck, originating tl Etanoochiaja." The latter 



is only found within a few yards of the contact of the two eruptive 

 rocks, and is therefore difficult to procure in considerable quantities. 

 It La streaked over with green and yellow markings, which anasto- 



like capillary blood-vessels. The margin of the euphotide in 

 contact with the Berpentine is often even and smooth, as it' Miction 

 had taken place ; frequently a Bpace of an inch or two may be seen 

 between the surfaces, evidently product d during the act of cooling. 



.War Matarana ( Ciguria), within a lew yards of the Berpentine I lie 

 euphotide contains crystals of diallage half an inch in length, their 

 size diminishing to a quarter of an inch at the junction with the older 

 rock- whence also i; is proved to be the newer of the two. In 

 receding in the contrary direction, the crystals of diallage are per- 

 fectly developed, and 1 .', inch long. 



III. DioriU (Greenstone). — Penetrating the former: like it, of 

 Eocene origin; may be seen in the neighbourhood of Miemmo, at 

 the bottom of the copper-mine of Monte Catini, (fee. 



The diorite and serpentine acting on the Eocene "macigno," a 

 micaceous sandstone, has produced the "gabbro rosso," a brick-red 

 schistose rock, in which the ancient stratification is sometimes clearly 

 visible, "though the rock is often broken up into fragments, rendering 

 it very difficult to obtain specimens a foot long without flaws. The 

 strata are extremely contorted, and in seme places have evidently 

 been bo altered by igneous action in contact with neighbouring rocks 

 as to have the appearance of having been themselves erupted. 



IV. Serpentint without Diallagt (locally termed "gabbro verd< "), 

 ■ — This reck is at once distinguished from the elder serpentine, as it 

 never contains diallage - silicate of magnesia preponderating. White 

 steatite' i- frequently found in it in Buch large quantities as to impart 



py feel : the absence of bronzite causes it to 1"- wanting in the 

 hardness and strength of the older serpentine. 



Being the first of a seri< - of phenomena of the Mi'» ene period, I 

 will describe it more fully. This " gabbro " is suffieientl] s 

 he quarried with a pickaxe, while the diallagic serpentini 

 to lie blasted with gunpowder. I t\ ted to the groat vi< iasitaai 

 Italian climate, the gabbro becomes very friable, the surface readfly 

 arumbles, and it weathers to a considerable depth ■■ a kind of steatitic 



