486 KEPORT ON NATIONAL MUSEUM, 1886. 



E.— QUARTZ PORPHYRIES. 



Eussia. — From the Isle of Hoghlaud, in the Gulf of Finland, the Mu- 

 seum has received a variety of quartz porphyries. These have mostly 

 a dull red, very compact base, and carry large, nearly white, pinkish 

 or reddish feldspars and glassy quartz in great profusion. The rocks 

 acquire a good surface and polish, but are intensely hard. Other por- 

 phyritic and compact rocks, variously called diorites, keratites, and 

 porphyries, were received from the district of Katharinenburg, in the 

 Urals, as noted in the accompanying catalogue of the collections. 



F.— SANDSTONES. 



(1) BRITISH PROVINCES OF NORTH AMERICA. 



Ontario. — On Vert Island, Nipigon Bay, in the northern part of Lake 

 Superior, Ihere occurs an extensive deposit of sandstone of Potsdam 

 age, in which quarries have been opened within a few years, and the 

 product of which has already found its way into the principal markets 

 of Canada and the Lake cities of the United States. The stone is of 

 fine and even grain, not distinctly laminated, hard, and of a bright red- 

 dish-brown color. It is said to occur in inexhaustible quantities, and 

 tliat blocks as. large as can be handled can be readily obtained. 



An 18-iuch cube from this locality in the collections of the National 

 Museum shows it to be one of the most attractive appearing of our red 

 sandstones. It cuts to a sharp and firm edge, and every appearance 

 would indicate it to be very durable, though possibly liable to fade 

 slightly on exposure. I am informed that its hardness is such that it 

 can not be sawn with sand in the usual manner, but must be cut either 

 with diamond-toothed circular saws or b}^ means of chilled iron glob- 

 ules. 



A thin section of the stone submitted to microscopic examination 

 shows it to consist of closely compacted grains of quartz and feldspar, 

 and an occasional shred of mica intersj)ersed with iron oxides, which 

 serve as a cement and give color to the stone. The feldspars are often 

 kaolinized and there is an occasional grain of calcite. 



New Bruns'wiclc and Nova Scotia. — Sandstones, varying in color from 

 red to yellow and light graj" with an olive-green tint, are very abun- 

 dant among the Lower Carboniferous rocks of Albert and Westmore- 

 land Counties in the province of New Brunswick. They are, as a rule, 

 soft enough to be readily cut when first quarried, but harden on expos- 

 ure.* So far as the author is aware the only one of these varieties ex- 

 tensively' used in the LTnited States is the olive-green from Dorchester, 

 Hopewell, and neighboring localities near Shepody Bay, at the head of 

 * Dawson, Acadian Geology, p. 248. 



