48 'School crafi's Localities. 



crystals of brown, or yellowish-brown foliated gypsum, va- 

 riously grouped. 



Compact Gypsum. — At Sandusky Bay, Ohio. This 

 gypsum forms a continuous stratum extending horizontally, 

 from the flat shore of the lake, near the Light House, into 

 the bed of lake Erie. It is situated so low as to be entire- 

 ly covered by the water during the prevalence of easterly 

 winds. It is of a uniform white colour, with a fine close 

 grain, and its surface presents very minute glimmering fo- 

 lia. It yields easily to the knife, or can be turned in a lathe, 

 and is sometimes so compact and hard as to take a polish. 

 These varieties may be considered a gypseous alabaster. 

 Some attempts have been made to convert this material in- 

 to inkstands, and other utensils. It has also been ground 

 for agricultural purposes, and if found to answer expecta- 

 tion, may become an article in the commerce of the Lake. 



Smoky Quartz. — At point Keewiiweenon,* Lake Supe- 

 rior, M. T. In a crystaline mass, associated with ame- 

 thyst. This mass separates with a blow of the hammer, 

 falling into innumerable translucent, dull crystals deeply 

 striated across the lateral planes, and sometimes terminated 

 by smooth six sided pyramids. The colour is not equally 

 intense, but often appears in clouds, and is sometimes in- 

 termingled with the violet hue of the amethyst. 



Amethyst. — With the preceding. Its colour passes from 

 violet to purple, and is seldom uniformly diffused. It is in- 

 timately connected with the preceding variety, and the 

 colours so mingled, in some pieces, as to make it difficult to 

 determine to which subspecies they ought to be referred. 

 I say subspecies, because, it would seem, from this connex- 

 ion, that the former is entitled to that destinction as well as 

 the latter ! 



Greasy Quartz. — At the Sault de Sfe. Marie, County of 

 Michilimackinac, Mich. Ter. In detached fragments, white, 

 opaque, laminated, and possessing the peculiar/cr/i^ lustre. 



Milky Quartz. — With the preceding. Neither of these 

 varieties has been traced in situ. I suppose them to be- 

 long to the primitive ranges along the north shores of lake 

 Superior. 



*Called Keweena in my Nar. Jour, and upon the maps of Sir Alex. Ma- 

 kenzie. The above pronunciation is taken from the Chippewa ludians 

 who inhabit the country. The double vowels are calGulated to convey 

 their long sounds. 



