NORTH UIST. MINERALS. 151 



pink and with a blueish colour, but the greater part 

 of it is milky. In many places the quartz which belongs 

 to the gneiss is grey and semi-transparent : in others it is 

 very dark, approaching to greyish black. In the same 

 place crystals of hornblende of three or four inches in 

 length are seen imbedded in quartz, and hornblende rock 

 is also found in large concretions in the gneiss on the 

 shores of some of these islands. These latter are often of a 

 singular appearance, being formed of a congeries of 

 crystals, loosely attached and, like coccolite, falling into 

 grains by a very slight force. In certain situations 

 garnets also occur in the gneiss beds. 



Of minerals unconnected with gneiss I observed none 

 but a species of bog iron ore accompanied by pyrites. 

 This is used by the natives in dyeing, with the assistance 

 of tormentil, galium, lichens, and other native plants ; 

 the uses and properties of which are familiar to the 

 Highlanders every where, as they are to the Tartars who 

 inhabit the plains of the Don. 



