1:90 



T. C. HOPKINS — CAMBRO-SILURIAN LIMONITE ORES 



The possible sources of the iron in the Cambro-Ordovician limonite 

 ores are I 1) the Lower Cambrian slates, where it occurs both as pyrite 

 and silicate; (2) the Cambro-Ordovician limestones and included slates, 

 where it exists as diffused carbonate, sulphide, and silicate; (3) theover- 



Jv\g*6«g Hudson ftiverS/afes 



"\Cimbro-Ordovician Limestones. 



o ,co? le °f feet 6f oo lilMUI) Cambrian Quartzi+e. 



$£A£&Arc/rean Scn/stS. 



Figure 6. — Map of Portion of Great Valley Region, western Part of Lehigh Count}/, Pennsylvania. 



Showing distribution of the limonite ore pits. Reduced from map in Report 1> I), Second Geolog- 

 ical Survey of Pennsylvania. 



lying Ordovician and Silurian shales and sandstones, where it occurs as 

 carbonate, sulphide, and hydrous oxide. 



Tt is well known that all strata contain more' or less iron, and those in 

 and bordering the limestone valleys of Pennsylvania are no exceptions. 



