KiNAHAN — On Granitic and oflier Ligcnite Rocks. 115 



other of the previously described schists, and eventually when more 

 highly metamorphosed they appear to lose their individual character. 



All the limestones and dolomyte'^' to be described are more or less 

 schistose, yet in many, the calcareous or dolomitic ingredients seem to 

 predominate to the nearly total exclusion of all others. This, however, 

 may be more apparent than real, and in such rocks the different foreign 

 substances may be amalgamated in the mass ; for the purest of these 

 limestones, as compared with the carboniferous limestones, give in the 

 proportion of 1 "5 to 2 '5 or 3 of lime, equal quantities of both being 

 burnt. 



The limestone may be white and of a saccharoid aspect. This is 

 sometimes a handsome stone, but in many cases it is impregnated with 

 pyrite or marcasite, and consequently, when exposed to atmospheric 

 'influence, it becomes discoloured. These white varieties occur in 

 various places, but the common colour of the schistose-limestone are 

 shades of blue and grey. The magncsian-limestone is usually white 

 or pale dove-colour ; the white rock is sometimes dolomyte, but not 

 always, as many are calcitic-dolomytes. The pale dove-colour rocks 

 seem generally to be a mixture of calcityte and dolomyte. Some- 

 times the calcityte will occur in streaks, layers, specks, or patches in 

 a dolomitic mass, or the dolomyte will similarly occur in relation to 

 calcityte. One variety of the dolomyte is a milk-white, compact, 

 homogeneous fine-stone, breaks with a conchoidal fracture, has exter- 

 nally the aspect of alabaster, takes a fine polish, but is hard and some- 

 what difiicult to cut. 



The pale dove-coloured dolomyte and the calcitic-dolomyte appear 

 to be the parent rocks of the ophiolytes and ophicalcytes, commonly 

 known as " Connemara serpentine or marble ;" both of these rocks in 

 places occur in mass. At the surface of the ground the purest rock 

 seems always to occur; some, apparently, answering Dana's description 

 of precious serpentine. This rock in depth seems to graduate into dolo- 

 myte and calcitic-dolomyte. Similarly at the surface ophicalcyte may 

 occur, while in depth it seems to merge into calcitic-dolomyte. The 

 colours of the serpentines are various, dark green, nearly black, pale 

 green, greenish yellow, streaked, ribaned, variegated, maculated, and 

 variolitic varieties having been observed, the combinations including 

 different shades of green, yellow, white, grey, and blue, with, on rare 

 occasions, red, separately or combined. f 



Associated with the ophiolytes and ophicalcytes are ophitic and 

 steatitic-scMsts, and in some places steatyte ; these sometimes are of con- 

 siderable thickness. There are also green unctuous schists that may 

 possibly be smwragdityte or smaragdite-schist.X 



* Dolomyte is the rock, dolomite the mineral. 



t Ophytes also are found in Yar-Connaught. They, however, are pseudomorphose 

 igneous rocks and will be described with them. 



X These latter rocks seem to be described by Cotta as a variety of eMogyte, but 

 typical eklogyte seems to be a pseudomoi-ph ingenite rock. 



