246 The American Geologist. October. 1904. 
been penetrated by a large number of deep wells, and having 
developed a thickness of nearly 2000 feet. It varies from 
gray (or greenish) to red, but its products under the action 
of a common drill always appear red. The earliest published 
'account of this formation is to be found in the second annual 
report of the Minnesota survey, where it was described in the 
record of the Belle Plaine salt well, where it was penetrated 
about 500 feet. Subsequently it has been encountered in every 
deep well sunk in this part of the state. It is spread out hori- 
zontally over a large area in Minnesota. It is somewhat in- 
terstratified with quartzyte downwardly and with sandstone 
upwardly, fading out in both directions by changing to such 
rocks. It extends to Sioux Falls in S. Dakota where it colors 
the till locally, being charged with iron oxide. It is mentioned 
in all the Minnesota reports that relate to this stratigraphic 
horizon. 
The Freedom formation, which is the iron-bearing member, 
"consists of a variety of rock, including slate, chert, dolomyte, 
and iron ore and all gradational phases between those kinds of 
rock." The dolomyte is said to be the most abundant of these 
varieties, and alone to compose -the upper part of the Freedom 
formation. Its thickness is 500 feet, but was probably at first 
much more than 500 feet. In ^Minnesota this hori- 
zon has not been distinguished, but the whole shaly mass 
above the quartzyte has been considered essentially as one 
formation. So far as known no dolomyte has been discovered, 
but in only three instances have drill cores, or drillings been ex- 
amined with care, and those pertained to the upper portions 
of the member, viz : the Belle Plaine Salt well, the Mankato 
deep well and the Glencoe well. The deep well at the Lake- 
wood Cemetary, at Minneapolis.* was sunk into the Seeley gray 
slate about 33 feet. The East Minneapolis deep well and the 
Manlcato deep well were limited to the upper portion of the 
Freedom formation. The Glencoe deeji well passed through 
315 feet of red quartzyte below the Hinckley sandstone and 
the Fond du Lac red sandstone, and again entered a red shale, 
in which the v,'ell stopped after penetrating it 230 feet.t This 
quartzyte is supposed to be the representative of the New Ulm 
* Final Report of the Minnesota Geological Survey, vol. ii, pp. 182-1S6. 
^ Atlas Volume of the Final Report, Minnesota Si/rrer, plate xxxvii, Mc- 
Leod county. 
