352 rocks. 



albitic granite. It also contains emerald, topaz, corundum 

 zircon, fluor spar, garnet, tourmaline, pyroxene, hornblende, 

 epidote, and many other species. 



Diorite is a rock of the granitic series, consisting of horn- 

 blende and feldspar. Color dark green or greenish-black 

 Cry talh'ne texture distinct. 



Granite is one of the most valuable materials for build" 

 ing. The rock selected for this purpose, should be fine 

 and even in texture, as the coarser varieties are less dura- 

 ble ; it should especially be pure from pyrites or any ore of 

 iron, which on exposure to the weather will rust and destroy, 

 as well as deface, the stone. The only certain evidence of 

 durability, must be learned from examining the rock in its na- 

 tive beds ; for some handsome granites which have every 

 appearance of durability, decompose rapidly from some cause 

 not fully understood. The more feldspathic are less en- 

 during than the quartzose, and the sycnitic (or hornblendic) 

 variety more durable than proper granite itself. The rock, 

 after removal from the quarry, hardens somewhat, and is less 

 easily worked than when first quarried out. 



Massachusetts is properly the granite state of the union. 

 New Hampshire and Maine also afford a good material. 

 The Quincy quarries in Massachusetts, south of Boston, 

 have for many years been celebrated. Besides this locality, 

 there are others in the eastern part of this state, between cape 

 Ann and Salem, in Gloucester-, at Fall River, in Troy, in 

 Dan vers ; also south between Quincy and Rhode Island, where 

 it is wrought in many places, as well as in Rhode Island, 

 even to Providence. The so-called Chelmsford granite comes 

 from Westford and Tyngsborough, beyond Lowell, and an ex- 

 cellent variety is obtained at Pelham, a short distance north 

 in New Hampshire. Masses 60 feet in length are ob- 

 tained at several of the quarries. They are worked into 

 columns for buildings, many fine examples of which are 

 common in Boston, New York, and other cities. 



Good granite is also quarried in Waterford, Greenwich, 

 and elsewhere, in Connecticut. 



The granite is detached in blocks by drilling a series of 

 holes, one every few inches, to a depth of three inches, and 

 then driving in wedges of iron between steel cheeks. In this 

 manner masses of any size are split out. There is a choice 

 of direction, as the granite has certain directions of easiest 

 fracture. Masses are often got out in long narrow strips, a 

 foot wide, for fence posts. 



