Discovered Rock at Sioux Falls, S. D. — Todd. 37 
reasonably free from cracks and seams, but containing joint 
planes wbich facilitate tbe quarrying of large blocks." 
"Similar rock is quarried at Addison Point and elsewhere 
in Maine, and is locally known as black granite. It is used 
wholly for monumental purposes." 
Professor Jas. H. Shepard of the S. D. Agricultural Col- 
lege, writes : "I am in receipt of your esteemed favor and also 
of the beautiful sample of black granite you sent me. I tested 
this sample with the most corrosive agents in my laboratory and 
find they have little or no effect upon it. This indicates that it 
will be valuable for ornamental and monumental purposes. Per- 
sonally I think the sample a fine one and if you can quarry it 
in blocks sufficiently large it will have a commercial value of 
no small proportions." 
To ascertain as far as possible the geological relations of the 
rock and to learn of its weathering properties from an inspec- 
tion of its outcrops, the writer visited the locality not long 
since. 
The rock was first discovered on land now owned by 
Brown, Ross and Lyon, in the southwest of the northwest quar- 
ter of section 11, loi, 49, about two miles northeast of Sioux 
Falls, and it was found to extend also on to the next quarter 
west, owned by !Mr. B. H. Lien, who has done the most in de- 
veloping it. An exposure is also reported as occurring in the 
bed of the Big Sioux about a quarter of a mile further west, 
but not accessible at the time of my visit. Boulders identical 
with this rock are said to have been found a little north of 
Brandon, but it is quite different from the igneous rock ex- 
posed on the Split Rock a little north of Corson and described 
bv Culver,* Hobbs and Beyer, f The boulders near Brandon 
may possibly have been transported from the locality dis- 
covered. 
The exposures under consideration are only a few rods 
from the Big Sioux and their highest point rises only about 
ten feet above the waters of that stream. About an acre is 
now exposed and by probing it is known to extend much far- 
ther at lower levels, covered by only a few feet of loose earth. 
No exposures of Sioux quartzyte are known nearer the gab- 
• Trans. Wis Acad. Set'., TOl. viii, p. 206, 1892, and Bulletin 1, S. D. Geol. 
Surrey, p. 36, 1894-. 
t iona Geol. SurYcy, vol. Ti. p. 79, 1898. 
