74 SUBSTITUTE FOR EMERY, 



XII. 



Account of some ferruginous Rocks serving as Substitutes for 

 Emery, By Mr. Blavier, Mine Engineer *. 



Slf c* s r ™ ATURALISTS are agreed in confining the name of 

 dered an essen- emery to a rock containing corundum ; but if we were to 

 tial part of comprise under this general term every matter capable like 

 the true emery of giving the highest polish and lustre to 

 metals, marbles, granites, and other substances necessary or 

 An iron ore useful in the arts, we might admit into this class the mica» 



tm 6 ,!*, 1 !~ ceous iron ore, which occurs in the hollows and on the sura* 



same purposes. " 



mit of the granitic table-land between the left bank of the 

 Aveyron and the Viaur. 

 Where found. This substance is found chiefly, and in the greatest abun* 

 dance, at the bottom of the mountain of Rodez. Its colour 

 is sometimes gray, at others of a deeper or lighter red, but 

 in either case its fracture is steel-grained. It occurs thus on 

 the banks of the brook of Briane, and at a little distance 

 from Boutonnet, in the commune and arrondissement of 

 Rodez. These ferruginous rocks exist in the hollows in 

 rounded nodules, and in masses, the weight of which some- 

 times amounts to upward of 5 myriagr. [about 1 cwt.]. 

 May we not suppose, that these nodules are nothing but 

 fragments separated from the veins, that appear of different 

 thicknesses through the quartzose schists deeply tinged with 

 iron, that form the higher hills? This situation is at present 

 well known along the Briane, and it agrees perfectly with 

 the different points, where this mineral has been turned up 

 by the plough. Thus similar blocks are found on the sum- 

 mit of the table-land, particularly in the domain of Puech, 

 and at the side of the monastery, directly south and oppo- 

 site to the mountain of Rodez. The same ferruginous rock 

 exists in separate and more or less bulky fragments on the 

 back of the hill, that forms the separation between the cal- 

 careous band of St. Radegonda and the schistous ground 

 that continues parallel with the left bank of the Aveyron as 

 far as the granitic hill of Levezon. On descending the 



* Journal des Mines, No. ill, p. »oi, 



north-east 



