15(5 The America )k (Geologist. SeptcmlxT, 1895 
rererred it to tlie Potsdam, and at a lat(M- date described Par- 
(idoxldes biirbvri and LiiHjiihi ciihinicl I'l'oui tlie red pipestoue 
clay at Pipestone, Minn., which is ii layer embraced in it. 
Probably there is no one who woidd call in (luestion the fact 
that this conglomerate and ([uartzyte are earlier than the Ke- 
Aveenawan erui^tive ag'e. This is owing to the nietamor])hism 
and upheaval to which it has been subjected, and to a general al- 
liance which it shows in other ways with the older rocks. That 
its age is post Aniniikie, i. e., post Upper Huronian, is shown 
by its contents. The writer once made, in company with 
Prof. K. I). Irving, a collection of the various sorts of rolled 
pebbles that occur in this conglomerate at New Ulm. One of 
the most common kinds is a sort of jasper, probably of the 
same variety as seen by Mr. Sweet in tlie conglomerate on the 
('hii)pewa river. On making thin sections of these jasper 
pebbles they are found to be very characteristically from the 
taconyte beds of the Mesabi range, or from the parallel strata 
of the Penokee range.' It may be thought by those who have 
not carefully studied the crystalline rocks, that a jasper is not 
a very sure guide to the age of the conglomerate in which it 
may occur as a pebble. But a little consideration will show, 
in this case, that there is no mistake. This is a peculiar jasi);M- 
— so ])eculiar that it has received the s])e(*ial name faconi/fe* 
Several thin sections are illustrated in Bulletin X, Minnesota 
survey, by Mr. J. E. Spurr (plates V, VI, VII and VIII) who 
considers this taconyte one of the stages of transformation of 
the ores of the Mesabi range from glauconite to hematite. 
Prof. Van Hise has illustrated others from the Penokee range 
in his discussion of the Penokee iron-bearing rocks (plates 
XXVI, XXVII and XXIX) but he gives a different explana- 
tion of their origin. Setting aside entirely "the question of 
their origin it is plain that they are peculiar to the upper 
iron-bearing member of the Lake Superior region. Such jas- 
per pebbles of course might be found in any later fragnuMital 
rock, through the transportations which the formations un- 
dergo as debris from older to newer strata. But if it be char- 
acteristic in its indigenous form of a certain horizon it will 
never be found in a conglomerate at a lower stratigraphic hori- 
zon. This is the case with this curious jasper. There are 
*H. V. WiNCHELL, Twentieth Minnesota report, p. 12i, 189.3. 
