Naming Rocks. 161 
Quartz—The mineral silica. It often occurs in 
veins, sheets and dykes, more especially in the older 
formations. It is of various colors, from pure white 
to gray, blue and even black. 
Siliceous Sinter—A white, gray, light-pink or blue 
powdery deposit of almost pure silica, which has been 
deposited from hot geysers and mineral springs. 
Crinoidal-limestone—A rock composed of the cal- 
careous remains of crinoids, shells, corals and other 
marine life. 
Chalk—A soft, white, calcareous rock, formed en- 
tirely of the crumbled remains of foraminifera and other 
marine fossils. 
Coral—A rock formed of the accumulated remains 
of the coral insect. 
Peat—A dark-brown mass of compressed marshy 
vegetation. It is used as fuel. 
The foregoing description of the more common 
rocks are aimed to assist the young miner in his work 
of identification, and to‘enable him to assign to each 
kind of rock its proper name wherever met with in na- 
ture. 
C. W. Moore’s *‘Practical Gnide for Prospectors, Explorers and Miners.” 
