1 82 The American Geologist. September, 1905 
shows small yellow crystals y 2 centimeter in length with 
the habit determined by the form f, — 2R (0221) unmodified. 
The other type shows larger crystals of "dog tooth" habit 
which are often several centimeters in length. These 
crystals like the others are of a pale yellow color ajid their 
habit is determined by d, — 8R (0881) with which is gen- 
erally present e, — l / 2 R (0112) and t, *4R 3 ( 2I 34) an d some- 
times v,"R 3 (2131). The faces are more or less dull, and 
frequently vicinal, but allow their angles to be read with 
sufficient accuracy for a determination of the forms. 
The celestite occurs in tabular to bladed crystals vary- 
ing in size from one-half to several centimeters in their di- 
mensions. The color is a pale blue, as in the case of the 
well known celestite from Put-in-Bay on lake Erie. The 
base is always the tabular plane and the macro-diagonal the 
axis of greatest development.' The forms present are, in 
the order of relative size, c, OOP (001) ; d, l / 2 V (112) ; o, Poo 
(on) ; m, oop (no) ; and z, P (in). 
The crystals of fluor spar are associated with the calcite 
and the celestite in the cavities. They are cubes and cubo- 
octahedrons made up of well-rounded sub-individuals, and 
sometimes attain to a size of two or more centimeters along 
the cubic edge. Some crystals are nearly colorless and 
quite clear; others have areas colored yellow, but the ma- 
jority of those examined have a rich brown color between 
that of smoky quartz and of the well-known brown siderites 
from Roxbury, Connecticut. 
A mineral much less common in the geodes is sphaler- 
ite, which appears in distinct crystals a centimeter or more 
in diameter. The color is that of a light "rosin jack" and 
would match the color of the well known sphalerites from 
Joplin, Missouri. Like the latter, also, the combination 
found upon the Tiffin sphalerite is that of the dodecahedron 
with the common trapezohedron (311). 
h. Calcite from Grand Rapids, Michigan. Specimens 
of calcite from Grand Rapids, Michigan were received from 
Mr. J. C. Ulman of Ashland, Wisconsin. He collected them 
in 1894. According to his statement the crystals are found 
in seams and cavities in the limestone which forms the bed 
