166 
EIGHTH ANNUAL REPORT. 
APPENDIX A.. 
[From the American Journal of Science, Vol. XIX, February, 1880.]. 
On Lintonite and other forms of Thomsonite: A 'preliminary notice of the 
Zeolites of the vicinity of Grand Marais, Cook County , Minnesota ; 
BY S. F. PECKHAM AND C. W. HALL. 
Grand Marais is situated on the northwest coast of Lake Superior, one 
hundred and eight miles northeast of Duluth. It is the site of an early 
French trading or mission station, and was later a station of the Hudson 
Bay Company. Its beautiful land-locked bay furnishes the only good 
harbor between Duluth and Pigeon Point. 
The rocks, for several miles east and west, as well as at the Marais, are 
classed in general as igneous, and have often a basaltic structure. They 
present, however, great diversities of character both to the chemist and 
lithologist; and while the mineral species are perhaps altogether old, the 
forms are in some cases new. It was our original intention to confine this 
research to one or two peculiar forms that first attracted our attention, but 
in the progress of our examination the subject has outgrown its earlier 
proportions, both as regards its extent and the time required for its 
successful completion. We have therefore concluded to give in the present 
paper some general observations with such details as are at present in hand, 
reserving others until further study and analyses shall have yendered the 
work more complete. 
At Good Harbor Bay, about four miles to the westward of Grand Marais, 
there begins a bed of dark colored rock, highly decomposed at surface, and 
related to diabase in its lithological characters. This bed extends westward 
along the coast for several miles, sloping gently from the wooded hilltops a 
mile or two inland, and disappearing beneath the waters of the lake In 
its fresher parts the rock is somewhat mottled where coarsest, and nearly 
black with a greenish tinge where finest in texture. It is only from the 
talus, under the wall of rock rising above an underlying sandstone outcrop 
in Good Harbor Bay, that this fresh material can be easily obtained. Even 
here the mottled appearance discloses the partial decomposition of the 
most perishable of the constituents, and the formation of some new viriditic 
mineral. The lower layers are firm and compact, while the upper are 
extensively jointed and fractured, and filled with amygdaloidal cavities, 
These cavities, in whatever manner they were originally formed, liave^ 
