460 ANNUAL. REPORT' OF THE Off. Doc. 



cial aid of the United States Geological Survey. While this work 

 is going on, something is being done by the Geologists of this Board, 

 one of whom has, during the past ten years, been serving as the 

 Geologist and Mineralogist of the Commonwealth. The service has 

 been principally what is known as economic — giving a practical or 

 commercial turn to geological subjects. 



BUILDING STONE. 



Part of the time during the past year has been devoted to build- 

 ing stone, large deposits of best quality being found here and there 

 in almost every county. Take, for instance, the first county, alpha- 

 betically, Adams. 



In Butler tovv'nship, within fourteen miles of Gettysburg, and 

 less than two miles from a railroad, were found two of the most 

 beautiful as well as durable granitic rocks that have been discovered 

 in America. The deposits are massive, and can not be quarried 

 out with a thousand men in a century. The lighter-colored, reddish 

 rock, with greenish prisms scattered through it, is a hornblende 

 granite. On analysis it was found to contain the following con- 

 stituents: 



Silica, (SiO.,) 77.60 percent. 



Oxide of Alumina, (ALO3,) 13.05 per cent. 



Oxide of Iron^ ( FeoO^,) 4.95 per cent. 



Lime, (CaO,) 1.90 per cent. 



Magnesia, (MgO,) 0.848 per cent. 



Manganese, (Mn,) 0.506 per cent. 



Sulphur, (S), 0.260 per cent. 



Loss on ignition, 0.52 per cent. 



99.634 per cent. 



Its specific gravity was ascertained to be 2.63. 



Some of the iron particles were magnetic. 



In the rock no pyrite, marcasite or pyrrhotite was found. 



No mica was discovered. 



The hardness of the rock was determined as 5^ to 6, or the* usual 

 hardness of first-grade granite. 



The samples herewith submitted show that the stone can be very 

 highly polished. 



This granite has been named "Pennypackerite," in honor of the 

 Chief Executive of our Commonwealth. 



The constituents of the darker rock are nearly the same though 

 in somewhat different proportions. It is technically an augite 

 syenite, with a small amount of quartz. This stone will be known 

 to science as ''Critchfieldite," in honor of our Honorable Secretary 

 of Agriculture. 



As a building stone, for exterior or interior work, there is proba- 

 bly no superior anywhere; and there is a peculiar beauty and attrac- 

 tiveness about it that will lead to a great demand for it for many 

 purposes. In the second Geological Survey report of the State, 

 this rock was noted on the map as "trap." The samples exliibited 

 herewith show the rock in all forms of dress by the granite cutter, 



