4 WILLCOX : 



is composed of silica combined with a little water, and it 

 is nearly similar in composition to the mineral opal. 



A variety of quart/, when green is called chrysophrase. 

 The dark colored flint stone, found abundantly in the chalk 

 beds of England and formerly used on the old fashioned gun 

 locks, consists of quartz. All the rock formations of the 

 earth, including the soils, consist largely of silica, both in the 

 free state as (juartz and in com])ination with other substances, 

 chiefly alumina. 



Aluminum, the second most abundant of the elements, 

 has lately assumed a prominence in the industrial arts. It is 

 the lightest in weight, as well as the most abundant of all 

 the metals. 



It is only successfully reduced from any of its combina- 

 tions by means of the intense electrical heat. The most 

 extensive works for the reduction of aluminum in America 

 are located at Niagara Falls. Aluminum is always found in 

 its natural state to be combined with oxygen, and in that con- 

 dition it is called alumina, which in its free state is a rare 

 mineral, not found at many localities. Corundum is the only 

 mineral consisting wholl>- of alumina. It is next to the 

 diamond in hardness, and in its crude form it is used only 

 as an abrasive material, superseding emery, which is an 

 impure corundum, consisting partly of iron. At two known 

 localities, viz : in India and in the island of Ceylon, corun- 

 dum is found in a condition suitable as gems. Some translu- 

 cent, six sided or hexagonal crystals, when polished, shcnv 

 six opalescent lines radiating from a central point. This 

 variety is used as an ornamental stone and is named the aste- 

 riated sapphire. When transparent, corundum is called col- 

 orless sapphire. When blue, it is sapphire merely. When 

 yellow it is called Oriental topaz, and it then excels the true 

 topaz in brilliancy. The red corundum is the (lueen of gems, 

 the ruby, the most beautiful of all minerals, and, when of 

 deep color, is more valuable than a diamond of the same size. 



We thus liiKl that aluniin;i, one of the iiiosi ;ibnn<l;iu1 sub- 



