298 NEW ZEALAND NATURE-STUDY BOOK 
(6) Particles arranged in different layers i.¢. rock is 
stratified. hat 
(c) Rock frequently contains marine organisms. 
Uses. The uses to which Sandstone is put depends 
largely on the hardness and texture of the rock itself, 
Some varieties—notably the Oamaru Sandstone — form 
excellent building material; others again, the harder 
varieties, are used for grinding purposes, and in many 
districts in New Zealand are employed as road metal. 
SHALE. 
The term Shale is here applicd to the finer grained 
fragmental rocks, and is used to include Mudstones and 
Clay-rocks as well as Shale proper. 
A Shale, then, we may define as a fine, more or less 
sandy or clayey rock, whether laminated or not, of varying 
hardness, 
The specimens for examination should include several 
varieties of Shale, both hard and soft, with one or two 
pieces showing lamination. 
Notice the general shape of the specimen and its colour, 
feel, taste, and odour. 
Select a soft specimen, scrape away some of the surface 
with a knife, collect and carefully examine the material so 
obtained. Empty some of it into a jar of clear water ; shake 
up and notice the turbidity of the liquid. Place some more 
of the material in a beaker, and having poured on just 
sufficient water to moisten it, work the whole up into a thin 
paste. Compare with the muddy deposits left on a sea- 
beach, or river-bed, or on the bottom of pools along the 
road. Hduce that the material being examined is fine 
clay or mud, and that the rock is a clay or mud rock. 
Supply the name shale, and compare and contrast the 
rock with Sandstone. Both are formed by agency of 
