i 



312 Scientific Geology. 



Limestone of Stontham and Newbury. 



In both these places the limestone is in irregular unstratified masses 

 in sienite, except that the most northerly bed in Newbury is in green- 

 stone. For the most part, the limestone is either finely granular, or 

 compact, and white. That at Stoneham is translucent on the edges ; 

 (No. 496.) and were it not for the numerous seams and cracks in it, 

 would prove a very fine article for statuary and other ornamental 

 purposes. Two or three quarries have been opened at each of these 

 localities, only a few rods apart ; but they are now abandoned. At 

 Newbury, the great amount of foreign minerals present renders the 

 limestone of little value, even for the production of quicklime. 



Among these minerals precious and common serpentine predom- 

 inate : and these being disseminated in the granular limestone, form 

 the ophicalce grenue of Brongniart,* which he mentions as occurring 

 at Newbury. f Specimens of this variety may be seen among those 

 that are polished in the collection ; (Nos. 896 to 899,) although the 

 geological position of this rock, if I have not mistaken it, is not 

 above organic relics (epizoique) as that author supposes it com- 

 monly is. 



Another beautiful mineral, often running in veins through the 

 ophicalce grenue, or the serpentine, varying in width from a mere 

 line to half an inch, is green amianthus. When a specimen is 

 newly fractured, this mineral presents a peculiarly rich appearance. 

 Its color is grass green and yellowish green. (No. 872.) Common 

 asbestus occurs in the same situation. 



Fibrous limestone, or satin spar, occurs in the same connection. 

 The fibres are sometimes four or five inches long, though the veins 

 of this mineral are quite thin. 



Tremolite in radiated masses is not uncommon in this limestone. 

 Epidote also occurs here in crystals ; and white and gray varieties 

 of compact feldspar. Associated with the tremolite and epidote, is 

 found massive garnet. 



The limestone at Stoneham is not so much mixed with other min- 

 erals as at Newbury. It occasionally, however, contains nephrite. 

 This mineral melts with great facility before the oxy-hydrogen blow- 

 pipe, and without difficulty before the common blowpipe, into a yel- 

 lowish slag or scoria. Another grayish green mineral occurs in 



* Classification des Roches, p. 96. 

 t Tableau des Terrains, &c. p. 325. 



