148 THE CRYSTALLINE ROCKS OE CECIL COUNTY 



Ruttie. — A reddish-brown transparent to opaque oxide of titanium, 

 occasionally found as fine plates or prisms in serpentines and other rocks. 



Sanssurite.— 



ScJiist. — A rock that has a parallel or foliated structure developed in it 

 by shearing through recrystallization of the constituents in parallel 

 layers. 



ScMstosity. — The secondary foliation or imperfect cleavage produced in 

 schists during metamorphism. 



Sedimentary. — Formed originally of sediments deposited in water or air. 

 The material is usually sand or clay derived from the debris brought 

 down by rivers. 



Serpentine. — A massive platy or fibrous hydrous magnesium silicate usu- 

 ally green in color. Also a rock composed principally of serpentine 

 derived from the metamorphism of basic igneous rocks, such as peridotite. 



Soapstone. — A greasy, grayish-green metamorphic rock composed prin- 

 cipally of the hydrous magnesium silicate talc or steatite. 



Staurolite. — A reddish-brown to brownish-black silicate of iron and 

 aluminum often crystallizing' in small crosses. 



Strike. — The direction of the intersection of an inclined bed of rock with 

 the horizontal surface compared with a north and south line. This may 

 be found by taking the direction at right angles to the greatest inclina- 

 tion or dip. 



Talc. — A greasy, greenish-white, hydrous magnesium silicate. In the 

 form of a rock often called soapstone. 



Tourmaline. — Usually a black, lustrous, complex silicate of iron, boron 

 and aluminum, frequently recognized by its triangular cross-section. 



Tremolite. — A light-colored often fibrous lime-magnesium silicate. 



Triclwism. — The property of a mineral by which it transmits different 

 colors in different directions. All of the colors are produced by the 

 varying proportions of three axial colors polarized at right angles to 

 each other. 



WiUiamsite. — A clear, more or less translucent variety of serpentine. 



Zaratite. — An emerald-green hydrous nickel carbonate found incrusting 

 serpentine. 



Zircon. — A zirconium silicate often found in minute crystals in gran- 

 ites and other rocks. 



Zoisite. — A vitreous gTeenish-white magnesium silicate of aluminum 

 frequently formed from the feldspar of basic rocks during metamorphism. 

 A variety of epidote. 



E. B. M. 





