Septembek 2, 1910] 



SCIENCE 



315 



ical classification, a Hessose and the closely 

 related Bandose and Auvergnose are the most 

 widely represented types. 



2. The table of mineral analyses shows the 

 degree of purity of the material found and 

 needs little explanation. Several of the oc- 

 currences are here recorded for the first time, 

 notably the datolite. Laumontite furnished 

 material for a crystallographic study now in 

 progress. The angles observed between the 

 simple prisms and oblique terminations are 

 too far from those recorded to be easily ex- 

 plained by the impurity of the mineral. Fur- 

 ther, an alteration of laumontite is found 

 clearly formed at a dump of a new deep shaft 

 on Snake Eiver. Coarse red laumontite 

 grades into light earthy green, especially 

 along contacts of two crystals or the coating 

 of caleite which is common on laumontite. 

 Well-developed pseudomorphs occur, retaining 

 the peculiar angles mentioned for the original. 

 A study of occurrence on the dump, indicated 

 that further alteration yielded a much lighter 

 green soapy to earthy product. Thin sections 

 show a confused aggregate, even in the pseudo- 

 morphs, none of the particles reaching one 

 hundredth of a millimeter in length, and none 

 showing a high interference color. The an- 

 alyses show that these are no simple minerals, 

 but they represent a remarkable substitution 

 in the laumontite. Lime is completely re- 

 moved, as is part of the water, while potassium 

 and magnesium increase. The variability in 

 similar material in other outcrops is also 

 shown. Tests are in progress to determine its 

 homogeneity if possible. It is proposed to 

 call it pseudo-laumontite. A mottled diabase, 

 altered very green, gave further evidence of the 

 prevalence of alteration to some mineral or 

 mixture high in potash and magnesia. Unless 

 this soft aggregate contains orthoclase, the 

 alteration is not previously recorded for lau- 

 montite. The solubility in sulphuric acid 

 makes orthoclase quite impossible. Dana men- 

 tions alteration by " magnesian solutions." 

 Van Hise' and Clarke' in discussing the 

 alteration of rock minerals mention no such 



' U. S. Geological Survey, Monograph 47. 

 *U. S. Geological Survey, Bulletin 330. 



products, but Pumpelly' speaks of a replace- 

 ment of many zeolites by chlorite, and a 

 pseudomorph of " clay ( ?) after laumontite " 

 which probably refer to similar material as it 

 is common throughout the Keweenawan. 

 iSTeither chlorite nor clay is an accurate name. 

 3. A study of the prospective copper de- 

 posits of the southwestern extreme of the 

 Keweenawan rocks led to a test of the country 

 rock for traces of copper. The common the- 

 ory of origin of the Lake Superior copper 

 deposits is that of lateral secretion from the 

 diabases, but both ascending and descending 

 solutions have been credited as supplying part 

 or all of the copper. Direct evidence has not 

 been found in the literature, except a refer- 

 ence to a few grains of sulphids in the fresh 

 diabase. The present tests are reasonably 

 conclusive. Copper does occur in all the main 

 types of rock, and as far as can be judged 

 from ten samples, the fresher the rock the 

 larger the amount of copper. The type of 

 rock shows less effect on the proportion of 

 copper than the alteration. An olivine rock, 

 high in the series on Snake Eiver, with hardly 

 alteration enough to yield chlorite, gave a 

 maximum, 0.029 per cent., and the altered 

 rocks a minimum, 0.012 per cent. Blank an- 

 alyses were made and all due precautions ob- 

 served. A test of the compound in which 

 copper exists gives signs of an insoluble sili- 

 cate, probably augite. Only one tenth of the 

 copper was soluble in nitric acid in the rocks 

 tested. A calculation shows that a concen- 

 tration of copper from 500 parts of rock to one 

 part of ore must have occurred to produce the 

 known ores from such rock. Such a concen- 

 tration, though extreme, is by no means im- 

 possible. 



Frank F. Grout 



Universitt of Minnesota, 

 January, 1910 



THE TOADS OF THE NORTHEASTERN UNITED 

 STATES 



Since the publication of the " Frog Book " 

 by Miss Mary C. Dickerson, in 1906, consid- 



° Michigan Geological Survey, Vol. I., Pt. II., 

 p. 4.5. 



