82 University Geological Survey of Kansas. 
The secondary flint usually contains ore and in many places 
well-shaped crystals of galena or blende are embedded in it, 
showing that it was formed almost simultaneously with the 
ore crystals or at a somewhat later time. Plates VIII to XV 
illustrate this peculiar combination of the two kinds of flint 
and to a certain extent the relation between the ore and 
the secondary flint. Cavities from which ore crystals have 
been dissolved are abundant in places where ground water 
is now dissolving the ore, as is shown in plate XVI. It is 
probable that the secondary flint is still forming at the present 
time. In many places we find it wholly or partly surround- 
ing beautiful garnet-like crystals of blende which have all the 
appearance of very recent growth. Brilliant-faced crystals 
of galena are occasionally found almost covered by a deposit 
composed principally of minute grains of quartz with a suf- 
ficient amount of cementing material to hold them together. 
During the spring of 1895 some choice museum material was 
found in the Chitwood Hollow mines, composed of brilliant 
galena crystals, some of which were partly covered with 
small calcite scalenohedrons and others largely covered with 
these sand-like masses which apparently are still forming. 
The secondary chert is in reality, therefore, a gangue ma- 
terial associated with the ores and is related to them in age 
similar to other gangue materials in different mineral veins. 
Its hardness varies with its composition, so that in many 
instances it is almost if not quite as hard as the primary 
flint. The firmness with which it cements together fragments 
of the primary flint is correspondingly variable. It may 
hold them so securely in place that fractures produced by 
earth movements break through the primary flint rather than 
to separate them from the secondary. Ore masses likewise 
are held in the firm grasp of the gangue material and - break 
accordingly. 
It should not be understood that all the cavities between 
fragments of primary flint are thus cemented, for in the 
richest mines, where ore is most abundant, the ore itself 
partly or wholly fills the cavities, sometimes to the entire ex- 
clusion of secondary flint. In other places, and in fact most 
commonly, secondary flint is so abundant that the ore is held 
