296 NEW ZEALAND NATURE-STUDY BOOK 
indurated, and should show, so far as hand specimens can, 
distinct evidences of stratification. 
Notice the shape and general colour of the specimens, 
Select a moderately soft coarse-grained specimen, and 
scrape away some of it with a knife. Examine the 
fragments carefully, and note that they consist of small 
hard angular or sub-angular grains. Compare with sand 
obtained from the sea-shore, or a river-bed, and ascertain 
that the mass is composed of sand-grains firmly 
cemented together. Refer again to colour—the sand- 
grains from the sea-beach are white, the rock is coloured 
red, brown, yellow, green—as the case may be—explain 
that the colouring matter lies in the cement. 
Contrast with some of the igneous rocks ¢.g. Granite or 
Basalt — notice that the latter is compact, dense, and 
consists of minerals—some of which show the form of 
crystals, all of which are imbedded in a hard matrix — and 
none of which can be rasped away from the rock without 
being injured—Sandstone, on the other hand, is made up of 
grains, of fairly uniform size and irregular shape, which 
can be detached with relative ease, and for the most part 
are composed of the same mineral. Igneous rocks are 
crystalline ; typical Sandstones are non-crystalline and 
fragmental ic. are composed of fragments which once 
belonged to other rocks. 
Cut into several of the specimens and notice the difference 
in texture or size of the particles, and in hardness. 
Educe that the latter is mainly due to the cementing 
material. Notice in some of the specimens the well 
marked stratification. 
Test for brittleness and notice that this differs with 
the specimen—also for cleavage, a property which is well 
marked in some varieties. Notice the uneven fracture 
and in most cases the absence of taste and odour. 
