90 H. S. Dana—Chondrodite from the Tilly-Foster Iron Mine. 
ally lined with more or less perfectly crystallized chondrodite, 
and also with dodecahedrons of magnetite, crystals of ripidolite, 
and rarely apatite, and then subsequently filled in with dolo- 
mite Where this has been the case and the dolomite has 
remained intact the chondrodite has been protected and the 
erystals have retained perfectly their brilliant luster and gar- 
net-red color. 
The species chondrodite is of especial interest because of its 
relation to the Vesuvian humite. As shown by Scacchi, and 
confirmed by vom Rath, the humite crystals are of three types, 
alike in the ratio of their vertical axes but differing in the 
length of the vertical axes. Chondrodite is identical with 
the types. 
1, Description of Crystals belonging to Type IT. 
Some difficulty was found in obtaining the value of the fun- 
damental angles from the fact that many crystals, though 
faultless in luster, yet gave uncertain measurements. This 
was due to the fractured condition of many of the planes, 
which, though often not very apparent even under a magnifier, 
i ey te 30 measurements of A(0=001) on r! gave: 185 
