AGATE. 



Agate is a form of the common min- 

 eral quartz. From other forms of that 

 mineral it differs in being made up of 

 minute layers and in being variegated in 

 color. The colors may appear in the 

 form of bands or clouds. The banded 

 agates appear to be made up of parallel 

 layers, sometimes straight, but more of- 

 ten wavy or curved in outline. These 

 layers or bands differ in color from one 

 another, exhibiting shades of white, gray, 

 blue, yellow, red, brown or black. To 

 the naked eye they appear to vary in 

 width from the finest lines to a width of 

 a quarter of an inch or more. In reality, 

 all the bands visible to the naked eye are 

 made up of finer ones, to be seen only 

 with the microscope. Thus in a single 

 inch of thickness of agate Sir David 

 Brewster, using the microscope, counted 

 seventeen thousand and fifty layers. Be- 

 sides differing in color, the layers differ 

 in transparency and porosity, and these 

 properties add to the variegated appear- 

 ance of the agate. 



On account of their beauties of color 

 and outline, agates have been known and 

 prized from the earliest times. They are 

 mentioned by many of the ancient Greek 

 writers, and the name agate is a cor- 

 ruption of the name Achates, a river in 

 Sicily, whence the first stones of this kind 

 used by the Greeks were obtained. This 

 and neighboring localities continued to 

 be the source of supply until the fifteenth 

 century, when agates were found to occur 

 in large quantities near Oberstein and 

 Idar on the banks of the river Xahe, in 

 the duchy of Oldenburg. 



The industry of cutting and polishing 

 the agates on a large scale was soon es- 

 tablished there, and these places are to 

 this day the center of the agate industry. 

 The agates used most 'extensively at the 

 present time are not, however, those 

 found about Oberstein, but come from a 

 region about one hundred miles in length 

 extending from the Province of Rio 

 Grande do Sul, of Southern Brazil, into 

 Northern Uruguay. 



The agates in this region, first discov- 

 ered in 1827, so surpass in size and 

 beauty those from any other known local- 

 ity, that they form at the present time 

 almost the only source of supply. They 

 are shipped in large quantities as ballast 

 to Oberstein and Idar, and here the work 

 of cutting, polishing and coloring them is 

 performed. The discovery that the at- 

 tractiveness of agates could be enhanced 

 by artificial coloring was made about the 

 beginning of the nineteenth century. The 

 natural colors are rarely of a high order, 

 being often only variations of white and 

 gray or dull yellows and reds. Through 

 the difference of porosity of the different 

 layers, however, and the consequent dif- 

 ferent absorption of coloring ingredients, 

 methods of artificial coloring can be em- 

 ployed, which produce lasting and pleas- 

 ing effects. Most agate used for orna- 

 mental purposes at the present time is 

 therefore artificially colored. 



Agates of considerable beauty, though 

 not of great size, are found in many 

 places in the United States. Those of 

 Agate Bay, Lake Superior, have rich 

 colors and make attractive charms and 

 other ornaments. Agates are found in 

 the beds of many streams in Colorado, 

 Montana and other regions of the Rocky 

 Mountains. They occur all along the 

 Mississippi River, especially in Minne- 

 sota, also along the Fox River, Illinois, in 

 the trap rocks along the Connecticut 

 River, and on the coast of California. 

 While many of these agates are of great 

 beauty, their use and sale is not likely 

 to be anything more than local, since the 

 Brazilian agates can be supplied so cheap- 

 ly from Germany. The moss agates of 

 Colorado and other localities in the 

 Rocky Mountains are. however, equal to 

 anything in the world. 



The layered structure of agates is due 

 to successive depositions of silica bv wa- 

 ter flowing through cavities in rocks. 

 Rising and falling alternately through 

 the rocks the water leaves a mark of each 

 advance or retreat in the form of an ad- 



