THE COLLECTION OF MINERALS. 
INTRODUCTION. 
MINERALS, in the broad sense in which science uses the term, 
include the air, the natural gases, water and the results of change 
in plant structures, such as coal, oil and resins. More popularly 
defined, minerals are those stony components of the earth which 
are to be found in its rocks and their crevices and which present 
similarity to one another in such characteristics as color, form 
and hardness. Most observers can easily separate Quartz from 
Calcite. In making the separation they associate with the idea 
of Quartz a certain lustre and hardness, a peculiar brittle and 
irregular fracture and, when the mineral is crystallized, a typical 
form quite in contrast with the same features in Calcite. A 
brilliant lemon-yellow crystal, or even a compact mass of Sulphur, 
is quite distinct in appearance from a greasy, black crystal or 
nodular piece of Graphite. The obvious physical characters of 
one are so different from those of the other that the most cursory 
examination serves to distinguish them as independent sub- 
stances. 
Such striking contrasts, however, do not exist generally in the 
mineral kingdom, and the observer usually is obliged to give 
more than a superficial examination to a mineral specimen in 
order to determine what it is. Most of the common minerals 
may be differentiated by simple tests with blowpipe and file, but 
all the rest, and they form by far the largest part of the whole 
number of species, must be examined by more elaborate chemical 
and physical means for their exact determination. 
The collection of minerals to which this Guide Leaflet is an 
introduction, though large and comprehensive, cannot be con- 
sidered an exhaustive representation of the mineral kingdom. 
It combines, however, in almost equal degrees the elements of 
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