38 Geology, ^c. of the Connecticut, 



The beds of this rock vary in width from a few inches 

 to 20 feet, and they rarely exceed this. They are un- 

 stratified, are sometimes traversed by veins of quartz, or 

 more frequently granite, and sometimes the rock becomes 

 so mixed with the mica slate, as to form one of its constitu- 

 ent parts. Rhombic crystals of carbonate of lime, of a 

 yellowish brown color, and agreeing by goniometrical ad- 

 measurement with the primitive form, are found imbedded 

 in this limestone, and sometimes these are connected 

 with irregular masses of quartz, and larger plates of mica. 

 It forms, when blasted, a good stone for underpinning. I 

 have never seen it along the Connecticut, except in the 

 mica slate at the northwest part of the map — none in any 

 part of New-England, nor in any mineralogical cabinet, — 

 yet it seemed to deserve a place on the map, and a descrip- 

 tion. 



11. Verd Antique.— C^eaiieZam?. 



Ophicalce Veinee. Brongniart. 



Colored blue, and marked with oblique parallel lines. 



The rich and elegant marble obtained from this rock has 

 induced me to give it a place on the map, although its ex- 

 tent is very limited. It extends northerly from Milford 

 harbour, 9 or 10 miles, apparently terminating two miles 

 west of Yale College. It constitutes an extensive bed in 

 chlorite slate, with which it sometimes alternates. I am 

 inclined, however, to the opinion, that the slate lying im- 

 mediately contiguous to the Verd Antique, although not 

 well characterised, approaches nearest to greenstone 

 slate. Yet, decided chlorite slate, appears usually only a 

 few rods distant. In some places, the Verd Antique is a 

 quarter of a mile in width, and forms ledges of considera- 

 ble elevation and extent. It is stratified — the layers being 

 thick and parallel to the slate rock enclosing it. The grain 

 is fine ; the rock is traversed by veins of calcareous 

 spar, magnesian carbonate of lime, and asbestus; and 

 is associated with chromate of iron and magnetic oxide 

 of iron, diffused, more or less, through the entire body of 

 the marble, and forming dark spots and clouds. The ser- 

 pentine is twisted and entangled in the limestone in almost 

 every form, and the green color of the rock may in gene- 



