86 ON THE MINERALOGY OF THE 



vecl horizontal divisions which the vertical strata 



exhibit. 



The colour of this stone is intermediate between 

 brownish purple-red and brownish-red. It is often 

 clouded with irregular spots of greenish-grey. 



The principal fracture, or rather structure in this 

 case, is irregular curved slaty. The surface of the 

 laminae is often spotted with dendritic delineations, 

 and is glimmering, owing to scales of mica, which are 

 in general obvious to the eye. The cross fracture 

 is fine earthy and dull. It is easily scratched with 

 the knife, and the streak is light-coloured and dull. 



This Brown stone exhibits several varieties of cha- 

 racter, according as the siliceous or aluminous earths 

 prevail. In the former case, the stone is coarse- 

 grained, thick, slaty and hard* in the latter, it is 

 fine-grained, softer, and divides into thinner la- 

 mina?. In some portions of the last variety, there 

 are galls of a brownish-coloured powder. 



This rock is intersected by numerous contempt 

 raneous veins of quartz, from the size of a thread 

 to upwards of a foot in breadth. In the lar- 

 ger veins, the quartz is compact, but in many of 

 the smaller veins it is parallel fibrous, the direction 

 of the fibres being perpendicular to the walls of the 

 veins. This is precisely the manner in which the 

 fibres of ice are arranged, when water has crystal- 

 lized in a narrow crevice. In some places the 

 quartz contains chlorite, and near Mallow Bridge, 

 I observed small quantities of iron-mica, 



