Jiev/ev: of JRecoit Geologleal Lif'rafui'r:. 205 
Geoloyicaf sitrni/ of Missouri. A'ol. II, L'e/iort on iron orcx, 1892. From 
field work prosecuted during the years of 1891 and 1892, with 62 il- 
lustrations and one map; by Frank L. Nasox, assistant geologist, 
Jefferson City, 1892. Roy. Oct. 366 pp. 
\o\. III. Jic/iorf on. fJir mineral watrrs of Mis.tonri ; by Pavl Schwicit- 
ZER, embodying also the notes and results of analyses of A. E. Wood- 
ward ; field and laboratory work conducted during the years 1890 to 
1892, with 45 illustrations and one maj), Jefferson City, 1892. Roy. 
Oct. pp. 256. 
These two volumes certainly show commendable progress in the 
development of the economical geology of Missouri. Mr. Nason has 
arrived at important results in respect to the origin and distribution, 
as well as the age, of the rocks and the ore which tliey contain. 
The ores of Missouri being either hematite or limonite, are confined 
practically, the former to the porphyry region, tlie Lower Carbonifer- 
ous and the Ozark series, and the latter to the 0/ark series.* 
A'ery full details are given of the localities where these ores are 
known, and particularly of all points at whicli some working has been 
done, (ieneral discussions are presented of the specular iron ores 
of the porphyry region, of the i-ed hematites, of the specular ores of 
the sandstone region, and of the limonites, also of the geology of the 
Ozark uplift. 
The specular iron ores of the i)orphyry region are those of Iron 
mountain, Pilot knob. Cedar hill, Sheplierd mountain and Clark's 
mountain. They are well known as the princi{)al ore deposits of 
Missouri. Here the ore occurs, primarily in veins and in isolated 
grains which is a rare method of merchantable iron ore ; but from these 
veins have been derived, through the decay and den undation of the 
porphyry, beds of conglomeritic debris which consists largely of 
blocks and boulders of hematite, and from these have been mined 
large quantities of the best hematite. The stratigraphic relations in- 
dicate that this disintegration took place sometimes in pre-Cambrian 
time, but has also gone on in more recent geologic ages ; these boulders 
are in the Cambrian and in the residuary clays of the Pleistocene and 
preseTit. The original veins are of all thicknesses, from mere films 
to forty and sixty feet. In places they form a perfect network in the 
solid porphyry. Iron deposits of like character also occur in the asso- 
ciated granites, but in general such have not yet proved sutticient to 
be of value. These hematite deposits in the veins of the i>orphyry are 
considered to be due to infiltration by percolating waters. The 
source of the iron is supjiosed to liave been the ore disseminated 
through the decayed and chiefly removed pori)hyry which once cov- 
ered the veins or which formed the surrounding country. This 
theory is ingeniously applied to Iron mountain and other prophyry 
knobs containing ore in veins. Wliile Mr. JSason is disposed to 
regard the rock of these hills as probably of sedimentary origin, he 
*For the signiticunceof the tt^nn "O/ark Series" see Amkkic.w Ge(ilioist, vol. ^'II1, i). 
33,1891. 
