Parr Lf. 
MINERALS AND ROCKS. 
I.—MINERALS. 
INTRODUCTION.—The earth’s crust is composed of mineral 
matter collected together and solidified in various ways and 
included under the general name of rock. It is difficult, perhaps, 
to realise at first that the entire crust of the earth with which we 
are acquainted either consisted or does consist of rock or mineral. 
Such is the case, however ; the soil on the hills and plains, the 
sand on the sea-shore, the mud on the river-bottoms and harbour- 
flats have all been derived from the earth’s rocky framework. 
Even the vegetable mould resulting from the decomposition of 
organic matter is indirectly indebted for its origin to the rocks. 
The disintegration of rocks or the way in which the hard 
material of which they are composed is gradually converted into 
soil will be dealt with further on. 
A rock is a mass of matter composed of one or more simple 
minerals, with a more or less irregular external form, and ranging 
in cohesion from loose debris to hard, compact, and close-grained 
stone. Granite, lava, limestone, sandstone, slate, shale, con- 
glomerate, breccia are all examples of rocks, 
As the rocks, themselves, are in nearly all cases merely 
agereeates of mineral matter, it is proposed before beginning a 
systematic investigation of rocks to examine a few of the 
commoner minerals. 
Minerals. A mineral may be defined as a substance 
having the same composition throughout formed by 
natural means, 7.¢., without the agency of man, and 
under conditions in which neither animal nor vegetable- 
life has taken part. 
