IGNEOUS ORIGIN OF LIMESTONE. 



49 



a. Linirslonp. 



Diagi-am No. 10 diflers from the preceding, principally from the connection which exists 

 between the vein and a liorizontal mass from which it proceeds. The veins which are dis- 

 closed in the rocks, and from which the diagrams are copied, appear in the face of ridges of 

 granite elevated but a few feet above the surface of the ground. They may be traced on tiie 

 surface very frequently for several rods, or until concealed by soil. They resemble the rami- 

 fication of granitic veins, and very rarely pursue the straight coiirsc of gi-eenstone dykes, 

 being more or less branching into smaller and thinner veins, and finally disappear or run out. 

 In this particular, the veins of limestone and granite resemble each other. 



The localities, of which so many have been spoken, furnish a great variety of simple 

 crystallized minerals. They are more perfectly developed at the junction of the two rocks. 

 Scapolite, hornblende, pyroxene and mica, are the most common to those localities. Brucite 

 is not connnon as in Orange county, and spinelle is still more rare, having never been found 

 at more than two or three places, and at those only in small indifferent crystals, yet in suffi- 

 cient quantity to show the complete and perfect analogy existing between the northern and 

 southern counties. 



The occurrence of foreign matter in the limestone is not 



^t,^ — V — -i— T~ ■^— ^-iTjrai ^^ ^^^ uniform. In some places, as has already been ob- 



fj .^^x i served, it is in the form of fine and perfect crystals ; in 



other instances, there is a teiidency only to crystallization, 

 or an effort to produce regular forms. In those instances, 

 the masses are strictly mixed or composed of particles of 

 augite, scapolite, and mica, which together form a rude 

 angular mass in the limestone ; and which, in consequence 

 of the feeble action of the weather upon them, stand out 

 in relief, as in diagram No. 11. 



Geol. 2d Dist. 



