DISTRIBUTION OF PYROCRYSTALLINE ROCKS. 
105 
variety of slate rock, which passes for clay slate, may he a 
variety of chlorite slate. Neither the mineralogist, geologist, or 
miner, has regarded the inquiries relative to the composition of 
rocks, veinstones, &c., of much importance, and hence they 
have been neglected. 
§ 75. Laminated limestone and serpentine. Where limestone 
and serpentine are associated with gneiss and mica slate, they 
exhibit a parallel structure. They have been acted upon by 
forces of the same kind and nature. We are not obliged to adopt 
the opinion that limestone and serpentine are metamorphic 
when we can detect a parallel structure. The facts in each 
particular locality must speak for us. For a full notice of this 
rock I refer the reader to § 65, the serpentine marbles. 
§ 76. Quartzite. I apply this term to a massive rock asso¬ 
ciated with the auriferous slates. It is smoke gray, light or 
dark, breaking with a conchoidal fracture, and hence resembles 
flint or hornstone. It appears to be a simple substance; but it 
becomes white by weathering, and hence it is probably com¬ 
pound. The quartzite contains sulphuret of iron, which may 
b$ auriferous. Some varieties are agatized coarsely. There 
is considerable evidence that the rocks associated with it are 
stratified, and hence it may be ranked among the metamorphic 
products. This question must remain open for further ob¬ 
servation. 
DISTRIBUTION OF THE PYROCRYSTALLINE ROCKS. 
§ 77. The pyrocrystalline rocks are blended and interlami- 
nated so frequently in every district of the United States, that 
it is impracticable at present to trace either of them separately 
through the range of country which they occupy. The White 
mountains in New Hampshire, mount Ktaddin, Maine; Monad- 
nock, New Hampshire; Hoosick mountain and Black mount¬ 
ain, and the culminating point of the Appalachians, are gneiss 
and mica slate. Many of the passes over the Blue ridge in 
North Carolina and Virginia, are talcose slate; Pilot mountain 
in Stokes, and Table rock in Burke counties, are talcose slates; 
