34 M. Mohs' Summary of Geognostical Phenomena. 



possess perfectly the above indicated features, and yet we per- 

 ceive that the repository intersects the structure of the rock and 

 of the rocky masses, and is consequently a vein and not a bed. 

 Among the useful minerals which occupy conformably the 

 space of whole repositories, although also mixed here and there 

 with the mineral substances occurring in these beds, are more 

 particularly to be mentioned iron-ores, including sparry iron, 

 iron-pyrites, and calamine. Lead-glance, likewise, and some 

 antimony-glance and manganese-ores, belong partly to this di- 

 vision. Among those, on the other hand, which are generally 

 obtained in combination with the mineral substances forming 

 beds, are to be reckoned, as the most general, the copper-ores, 

 especially copper-pyrites and grey copper-ore (Falderz), and 

 likewise sparry iron, inasmuch as it often occurs along with 

 copper-ores as they do with it, in one and the same repository. 

 True ores of silver, without including mere argentiferous ores, 

 seem to be rare in beds ; but still, little can be said with cer- 

 tainty on this head, because it is often difficult to decide posi- 

 tively whether a repository is to be considered as belonging to 

 the beds or to the veins ; any gold which may occur in veins is 

 generally associated with quartz, and is frequently so intimately 

 and finely united with it, that we can only recognise the actual 

 presence of the gold by the colour passing into grey, and by 

 the other properties of the quartz, which generally has less 

 transparency and lustre than it is wont to possess in similar or 

 analogous repositories, where it is not auriferous. 



In many beds, the ores and mineral substances are ar- 

 ranged together as it were in groups, and thus form me- 

 talliferous and barren points (erz mid taube mittel). After 

 one has carefully observed these metalliferous and barren por- 

 tions, regarding which no general statement can be made, he 

 can recognise their appearance and disappearance, before reach- 

 ing or traversing them by means of boring or mining. This 

 is important for the investigation and excavation of reposito- 

 ries, and a great portion of the peculiar skill of the practical 

 miner is founded on observations and determinations of this 

 kind ; it does not, however, belong to a place where the objects 

 under consideration are merely the search for and discovery 

 of these repositories. However, it leads to another subject 



