GLOSSARY 



OF SOME 



GEOLOGICAL TERMS, 



CHIEFLY FROM MATHER'S GEOLOGY 



A. 



Alluvial. The adjective of Alluvium. 

 Alluvion. A synonyme of Alluvium. 



Alluvium. Recent deposites of earth, sand, gravel, mud, stones, 

 peat, shell banks, shell marl, drift sand, &c, resulting from 

 causes now in action. This term is generally applied to those 

 deposites in which water is the principal agent. 



Alum rocks. Rocks which, by decomposition, form Alum. 



Amorphous. Bodies devoid of regular form. 



Amygdaloid. A trap rock which is porous and spongy, with 

 Tounded cavities scattered through its mass. Agates and simple 

 minerals are often contained in these cavities. 



Anthracite. A species of mineral coal, hard, shining, black, 

 and devoid of bitumen. 



Anticlinal. An anticlinal ridge or axis is where the strata 

 along a line dip contrariwise, like the sides of the roof of a house. 



Arenaceous. Sandy. 



Argillaceous. Clayey. 



Augite. A simple mineral of variable colour, from black 

 through green and gray to white. It is a constituent of many 

 volcanic and trappean rocks, and is also found in some of the 

 granitic rocks. 



Avalanche. This term is usually applied to masses of ice and 

 snow which have slidden from the summits or sides of mountains. 

 It is now also applied to slides of earth and clay 



B. 



Basalt. One of the common trap rocks. It is composed of 

 augite and feldspar, is hard, compact, and dark green or black. 



