Featherstonhaugh s Geological Report. 29 



subordinate to the statuary marble : this is the variety called 

 cipolino. In Connecticut extensive veined beds occur, trav 

 ersed by serpentine. In Maryland, several varieties occur, 

 and amongst others a paste of fine saccharine limestone, im 

 bedding crystals of hornblende, resembling that mentioned by 

 Mr. McCulloch* in the Isle of Tirey, Hebrides. 



Hornblende rock abounds in this country on the Atlantic 

 frontier, sometimes dark and compact, with a granular texture, 

 at other times greenish, with a fibrous structure, and disposed 

 to fissility ; it is sometimes micaceous, and near Wilmington, 

 at Quarry ville, on the Delaware, a locality which has supplied 

 the greater part of the materials for the Delaware break 

 water, there is a beautiful resplendent variety of ovate 

 lamellar crystals of felspar, having a slightish red color, with 

 a hornblende base, which fuses into a fine dark enamel. This 

 is a true porphyritic greenstone. 



The talcose slates have a base of talc, with mica and crys 

 tals of sulphuret of iron diffused in them ; they are easily 

 recognisable by their unctuous touch and glossy appearance. 

 In the United States these slates are largely developed in 

 what is called the gold region, especially in Virginia, the 

 gold being in the ferruginous quartzose veins w r hich traverse 

 this formation. 



The Germans have called all combinations of hornblende 

 and felspar, when they have a granite structure, grllnstein 

 or greenstone rocks, and accordingly, as they are compact or 

 fissile in their structure, they have been designated as primi 

 tive greenstone or greenstone slate. Hornblende is heavier 

 than quartz or felspar, and, when scratched, gives a light 

 green streak, and where it forms the principal part of rocks, 

 they take a greenish black color. In hornblende slates the 

 felspar itself is often green. When the quantity of magnesia 

 is increased in the hornblende rocks, they appear to pass in- 



* McCulloch s Western Islands, vol. 1, puge 50. 



