Report on the Tin of Piriac (department of the 

 Loire Infer ieure ) , hy Jilessrs Junker and 

 DuFRENOY, Assistants to the Royal Mining 

 Corps* 



(Annales des Mines for 1819.) 



The rocks of the coast from St. Nazaire to the mouth of 

 the Vilaine, comprise two distinct but primitive formations. 

 The first entirely granitic, extends from St. Nazaire to about 

 two kilometres [8000 feet] on the S.S.W. of Piriac. ^ 



The second, which is schistose, forms nearly the whole 

 cf the remainder of the coast. It is at the separation of these 

 two formations, that is to say, at the northern extremity of 

 the granite, that the oxide of tin is met with. 



Granitic Group, 



The granite of St. Nazaire, Guerande, and Croisic, is 

 generally small grained, of a brownish grey colour, with 

 black mica, often traversed in every direction by numerous 

 veins of fetid quartz. It sometimes contains crystallized 

 tourmaline (schorl?) as also felspar. In some situations 

 (at Turballe and Clis), the latter is found alone with the 

 quartz, producing the mineral named graphic granite, which 

 occurs in the most ancient rocks. 



* I have extracted only that part of this Report which gives a geo- 

 logical sketch of the country in which the tin occurs. (Tran.«.) 



