ECONOMrCAI. MATERIALS. 421 



and of a quality suitable for the best drawing pencils, but not in sufficient abundance to give 

 it a commercial value. The demand for this article is now so great, that careful search for it 

 is warranted. 



Precious stones. The zircon of Rossie is in sufficient perfection for cutting and setting in 

 all ornamental work, as rings, bracelets, broaches, etc. The black quartz, in dodecahedral 

 crystals, is sometimes handsome, and may possibly be found in the iron mines in sufficient 

 perfection to admit of being employed in ornamental work. The finest materials for these 

 purposes, however, is the labradorite, which may be obtained in large pieces. One or two 

 fine specimens of calcedony have been found in the trap dykes, which were truly gems. 



The preceding list of substances is inserted for the purpose of pointing out several mine- 

 rals, which would be accounted abroad as worthy of special attention. The list of natural 

 productions which are used in the arts is daily enlarging, and soon very few of them will be 

 passed by with indifference. 



The iron ores do not appear in the above list, as they have been described so fully, that all 

 the facts in relation to them have been stated. 



