1040 ■ Transactions of the American Institute, 



lime, it is called marly sandstone. If the quartz or sand pebbles are 

 rounded, and are held toj^ether in a conglomerate, the result is called 

 a pudding-stone; and if they are angular, a breccia. 



Tiie flexible sandstone, or itacoluniite, is a schistose quartz rock. 



Buhrstone is a cellular silicious rock. 



The millstone, or gritrock, is composed of siliceous pebbles. 



Siliceous schist is a flinty quartz rock. 



Jasper rock is likewise a flinty siliceous rock. 



Obsidian volcanic glass, or pumicestone, pitchstone, pearlstone, are 

 all siliceous or sandy rocks, having a volcanic origin. 



Sand, if transparent, bears the name of quartz, the constituent of 

 a great many rocks, of both the primitive and newer formations. 

 Quartz crystallizes in six sided prisms, with no apparent cleavage, of 

 all degrees of transparency and opacity, and of all colors, from 

 M-hite and yellow green to black, with intermediate amethystine, rose 

 and smoky tints. Pure pellucid quartz is called rock crystal, or pure 

 silica. 



Quartz is infusible before the blow-pipe, but when heated with 

 soda, fuses easily to a glass. If quartz has colored bands, it is called 

 ao-ate, and without bands or clouds, it is chalcedony. When mas- 

 sive, of dark and dull color, with translucent edges, it is called flint ; 

 if Math a splintery fracture, it is hornstone, like the Arkansas wdiet- 

 stone. When it is still more opaque, or black, it is the Lydian stone 

 or basanite ; of a dull red, yellow or brown color, and opaque, it is 

 jasper ; when in aggregated grains, it is called quartzite, and when 

 in loose, incoherent grains, it is the ordinary sand, which is frequently 

 transparent. Sandstone belongs to all ages, from the lower silurian 

 to the most recent period, but the azoic rocks, which are nearly all 

 crystalline, contain some sandstone; and the metamorphic, which 

 are the most ancient rocks, and comprise granite, gneiss and syenite, 

 consist largely of quartz. Certain dark red sandstone are known as 

 the freestone of Kew Jersey and Connecticut, and the general term, 

 new red sandstone is applied to this formation, which is more recent 

 than coal, while the old red sandstone lies below the coal, and above 

 the "Teat laurentian formation. Freestone is an excellent building 

 material ; in Xew York it is used more than any other stone. Trinity 

 church, in Broadway, and many other public and private buildings, 

 serve as examples ; also the greater part of the flagstones wliicli are 

 brought to this city from Connecticut. 



The green sand of Xew Jersey, which has for the last thirty years 



