804 M. Mohs oti the Discovery of Useful Minerals. 



ture of the mountain-masses and of the rock, and especially 

 if the mountain-mass is otherwise pretty free from them, wc 

 must allow ourselves to be guided by them. 



An acute observer will easily make out the modes of pro- 

 cedure, which in some other kinds of repositories can be em- 

 ployed in their investigation, when their first traces have been 

 discovered ; and it only remains for me to add some observa- 

 tions in regard to veins, as the discovery and examination of 

 this description of repositories are often combined with great 

 difficulties. 



The outgoing of veins is not unfrequently so indistinct, that 

 we can hardly make out what it really is. It often consists only 

 of decomposed vein-stones, without traces of ore, and is com- 

 posed of masses of mere clay or loam ; and sometimes appears 

 as a mere cleft, or several clefts, between whose walls hardly 

 any substance can be remai-ked. We can pretty easily dis- 

 tinguish an actual vein-cleft, which is the outgoing of a vein, 

 from an ordinary surface of a distinct concretion, or from a 

 smooth surface {Blati^ \ but the discrimination becomes moi'e 

 difficult when, as not unfrequently happens, a surface of a 

 distinct concretion, or a smooth surface, is combined with it. 

 In such a case we must attend particularly to the adjoining 

 rock. If it is fresh, that is, in its normal condition, as is almost 

 invariably the case with mere surfaces of distinct concretion 

 and smooth surfaces (Bldtlern), the cleft, although different from 

 surfaces of distinct concretions {^iisammensetziuu/s-fldcheii), is 

 nevertheless not a vein-cleft ; if, on the contrary, at a greater 

 or less distance from the cleft, it is altered in its constitution as 

 to colom", hardness, compactness, &c. and if this alteration dis- 

 appears the further we proceed from the cleft, so that we may 

 conclude that it proceeds from the cleft, and is produced by it, 

 then it is probably a vein-cleft. These are the most doubtfid 

 appearances. If we find vein-stones in the outgoing ; if the 

 latter is of some size, and if we meet with traces of py- 

 rites or ore in it, we have greater security ; and if the vein 

 appears with the usual peculiarities of these repositories, we 

 are still better off. Such cases require no further facts to 

 enable us to form our judgment and our plan of operations. 



Tn the doubtful cases we must employ every means calcn- 



