E. S. Dana—Chondrodite from the Tilly- Foster Iron Mine. 89 
Art. XVI.—On the Chondrodite from the Tilly-Foster Iron Mine, 
Brewster, New York; by Epwarp S. Dana. With plates 
V, VI and vi1.* 
THE method of occurrence of the Chondrodite at the Tilly- 
Foster iron mine, near Brewster, Dutchess Co., New York, has 
been fully described by Professor Dana in a memoir on the 
Serpentine and other pseudomorphs of the region.+ It may be 
of interest, however, to review the subject again in this place. 
e chondrodite forms the gangue of the magnetite, being 
everywhere disseminated through it in varying proportions. 
Tn the parts of the mine where the ore is purest and _ perfectly 
firm and solid,- -the so-called ‘ blue ore ”—the associated chon- 
drodite is sparsely sprinkled through it in small yellow grains, 
showing no trace of crystalline form. 
Tn the larger portion of the mine as now opened, however, 
the soft “yellow ore” predominates: the chrondrodite is present 
in it in much larger quantities, and, like the other associated 
large number of these products of alteration have been 
described by Prof. Dana in the memoir alluded to. The chon- 
ite in this “yellow ore” is generally massive; but occa- 
tion of them is seldom possible, but a few of the crystals found 
allow of it, and the results are described beyond. The form is 
usually very simple, and the color varies from a deep red to a 
light yellow. : : 
Material much better adapted for erystallographie study also 
occurs, though this is rarely true. toe veins are some- 
times met with, two or three inches across, which were origin- 
ract of a memoi lished i i ions of the Connecticut 
Academy of Sciences, vol ve ce 67 to 95, created ie ie place by the author. 
¢ This Journal, ITT, viii, 371, 447, 1874. 
