DESCRIPTION OF SPECIES. 



CLASS I. ELEMENTS. 

 Diamond. C. Regular. 



At various places north of Chicago diamonds have been found in 

 the drift. Prof. Hobbs describes seventeen specimens weighing together 

 about seventy carats. The largest weighed 21 ]i carats. They are most 

 commonly white or faintly green or yellow in color. They were found in 

 the sand and gravel of kettle moraines or in the beds of streams. Their 

 occurrence in seven localities north of Chicago may authorize us in 

 expecting them nearer at hand, and in the hope of promoting their dis- 

 covery mention is made of them here. 



If a small round transparent glassy or adamantine mineral of light 

 color is found it would be well to test its hardness. If it scratches every- 

 thing available, its hardness is probably ten; and if upon weighing, it 

 proves to be three and a half times as heavy as its bulk of water, it may 

 be pronounced a diamond. The finding of a diamond in this vicinity, 

 though of no financial value, might still be of interest as aiding the com- 

 pletion of lines leading to a possible common mother lode. These lines, 

 as now completed by Professor Hobbs (See "Diamond Field of the 

 Great Lakes," Hobbs, J. of Geol., Vol. VII, No. 4, 1899.) are given in 

 Fig. i. 



Graphite. C. Hexagonal. 



Carbon appears in this region as graphite in scales and 

 flakes in metamorphic rocks, chiefly gneisses, brought down by 

 glaciers from the north. These flakes are opaque, black in 

 color, of a greasy metallic luster, flexible, inelastic, and soft. 

 Their hardness is I in the scale. Their lack of elasticity and 

 their extreme softness enable us to distinguish them readily 

 from biotite flakes which are elastic and from magnetite scales 

 which are hard. They are infusible and unattacked by acids. 



Sulphur. S. Orthorhombic. 



In the interior of decomposing marcasite a crumbling 

 mass of sulphur is sometimes foynd. These masses are of so 

 slight a consistency as to make crystallographic determination 

 impossible. The more nearly oxidized they are, the more 

 spongy and powdery do they become. They yield sulphur 

 fumes in closed tube, are insoluble in acid, but/dissolve readily 

 in carbon clistllphide. In color they are a whitish yellow. In 

 luster earthy. Their hardness and specific gravity are unrelia- 

 ble because of their chemical condition. This sulphur, being 

 a secondary product of marcasite, which is native to the Niag- 



