BLUE PORPHYRY. 



193 



C^« Wl^ 



GladLoht? 



tragments are ' i-^ 

 turned to account for road- 

 making. Tlie whole shore 

 is littered with blue porph\'r\', 

 y and numerous work- 

 men are bus^• load- 

 ing ships with it. 

 The porph^•r'\• of the 

 Estercl is a cjuartz porph^■r^' 

 which has cr} stals, or crystalline 

 grains, of quartz and felspar imbedded in 

 a uniform matrix of the same substance, which 

 however are not distinguishable to the naked 

 e^-e. The felspar is generall}^ pinkish, but 

 the red colouring of the whole stone is produc- 

 ed chiefl\' hv oxide of iron which is distributed 

 in the form ot fine dust through the matrix. 

 In the blue, and other brightl\' coloured por- 

 phyry", combinations of protoxide ol iron have 

 replaced the peroxide. The blue porphyry is 

 much valued for road-making, and it is exten- 

 siveh- worked here. Opposite the quarry a 

 tongue of land, "Le Piton du Drammont", pro- 

 jects into the sea. Here, on steep rocks, stands 

 a high lighthouse. It warns sailors at a great 

 distance of the danger of this rocky coast. The 



