578 THE GEOLOGY OF MINNESOTA. 



[Cretaceous lignite. 



that it showed a great deal more of the real charcoal than any other point discovered. Some 

 fragments that lay near the opening, contained about nine parts of light charcoal to one of ash, 

 the whole very slightly cemented, and so frail as to hardly endure transportation. In this drift 

 were also numerous pieces of what is described by the owners both here and at Crow creek, as 

 'stone coal.' It is the same as that mentioned as probably a cannel coal, occuring at Crow creek. 

 It is these harder lumps that are found scattered in the drift thioughout the southwestern part 

 of the state." 



This mining was done in 1868 or 1869, on the northwest or left side of the Redwood river, 

 about one and a quarter miles north from Redwood Falls, on the south part of the S. W. J of 

 section 30, Ilonner, the hight of the drift being some 75 feet above the river, and about the same 

 amount below the top of the bluff and general surface of the country. The lignitic bed is reported 

 to dip slightly toward the southwest, and to be overlain conformably by shale, above which the 

 upper part of the bluff is till. Next below the black coaly bijer, is said to have been a marl, 

 varying from reddish to white, six inches to two feet in thickness, underlain by yellow and blue 

 clay. No exposure of gneiss or granite is visible at this locality. 



Specimens from the lignite and lignitic deposits thus mined near Crow creek and Redwood 

 Falls, and another from an outcrop of lignite west of Bismarck, in Dakota, were analyzed by 

 Prof. S. F. Peckham. In the list of samples submitted for analysis, these are numbered and de- 

 scribed as follows: 



"No. 11. Cretaceous coal, cannel, from Crow creek, near Redwood Falls, Minn." 



"No. 12. Coal, from the surface, near Bismarck, D. T., having the same external charac- 

 ters as the last." 



"No. 13. Earthy coal, from Crow creek, near Redwood Falls, Minn." 



"No. 14. A mixture of charcoal and ash, apparently, from the lignite beds of the Creta- 

 ceous, at Redwood Falls, Minn." 



Professor Peckham writes:* "The specific gravity was first determined by sifting the dust 

 from the finely granulated coal and weighing in a sp. gr. llask, after standing under water at 

 least 12 hours. One gramme was then weighed in a platinum crucible and dried at a tempera- 

 ture of 215-220 Fahr. until it ceased to lose weight. The loss is water. 



"The residue was then heated over a Bunsen's burner for 3.5 minutes, and then over a blast 

 lamp for the same length of time, and weighed. The loss was considered to be volatile com- 

 bustible matter. The residue was burned to an ash and the ash weighed. The loss from com- 

 bustion was considered to be non-volatile combustible material, or fixed carbon. 



"The coals are quite unlike. Nos. 11 and 12 are semi-cannel coals. No. 13 consists of a 

 mass of clay containing carbonaceous matter. No. 14 consists of an earthy mass, chiefly silica, 

 containing fragments of mineral charcoal. 



"No. 11 is homogeneous and brittle, of a dull black color, and cracks in a dry atmosphere. 

 When heated it is non-caking, the pieces retaining their form and size, and in this respect it re- 

 sembles some of the Cretaceous coals of the Pacific coast. The results of analysis are as follows: 

 Specific gravity, 1.441. 



Water 13.53 per cent. 



Volatile combustible matter 54.1 1 " " 



Fixed carbon 29.49 " " 



Ash 2.87 " " 



100.00 " " 



The total amount of combustible matter in this coal is 83.60 per cent. 

 "No. 12 in some respects resembled No. 11. It is a semi-canuel in appearance, very friable 

 in dry air, and non-caking. The results of analysis are as follows: 

 Specific gravity, 1.425. 



Water 12.70 per cent. 



Volatile combustible matter 38.32 " " 



Fixed carbon 45.61 " " 



Ash 3.37 " " 



100.00 

 The total amount of combustible matter in this coal is 83.93 per cent. 



*Fifth annual report, p. 57. 



