64 Review of M. Tuomexfs Final Report 



cropping edges of the rock, that extends from its southern limit 

 to the mountains." 



The outcropping edges of this rock, it is stated may be traced 

 across the state from the Savannah to the Broad river by parallel 

 ranges of natural dams which they form in the rivers, and over 

 which the water flows, forming picturesque cascades of from ten 

 to eighty feet in height. These phenomena Mr. Tuomey thinks 

 are due to the result of the alternation of more and less destruc- 

 tible beds, the former of which have been washed away, leaving 

 the latter projecting; rather than to a series of uplifts. The 

 strike of these rocks is northeast and southwest, and their dip 

 very nearly that of the Atlantic slope, excepting in a few instan- 

 ces at the southern extremity, where they have been elevated so 

 as to dip in an opposite direction. 



Hornblende slate. — This rock alternates with the gneiss in 

 some localities and passes into it. Its extent is limited compared 

 with the gneiss in mica slate. 



Mica slate. — Mica slate alternates with both hornblende slate 



and gneiss. In the extreme northwest of the state, it is the 



prevailing surface rock of the rounded hills of that region. It 

 passes into talco-micaceous and talcose slates by the substitution 

 of talc for mica. These latter rocks are found only in the gold 

 regions of the state, and in a belt in York and Spartanburg dis- 

 tricts that contains magnetic iron ore. 



Clay slates. — An extensive deposit of these slates occurs along 

 the northern boundary of the tertiary, from the Savannah river 

 nearly across the state, finally disappearing at the north under 

 the new red sandstone. 



Limestone. — Beds of limestone are found both in the gneiss 

 and mica slate, and are quarried to some extent for agricultural 

 and architectural purposes. 



Quartz rock. — The rock so designated is a stratified deposit, 

 and differs from the common massive quartz in its granular 

 structure, though it is sometimes compact and resembles the 

 common variety. It is associated with the mica and talcose 

 slates and passes into them. It seems, says Mr. Tuomey, to be 

 the result of the gradual disappearance of the matter forming the 

 micaceous or talcose portion of the rock in which it occurs, and 

 the introduction of a proportionably large amount of siliceous 

 or arenaceous matter during its deposition. One of the varieties 

 of this rock is the itacolumite, or flexible quartz. This variety 

 is found at some localities in this state, and also in the neighbor- 

 ing states of North Carolina and Georgia. It is known as the 

 repository of the diamond both in Brazil and the East. None of 

 these gems have as yet been found in South Carolina, but as our 

 author remarks, thousands may have escaped with the refuse 

 gravel at the gold mines. Both in North Carolina and Georgia 



