QUARTZ (AGATE): OCCURRENCE IN SOUTH AMERICA 5x5 



The size of the agate amygdales of course depends upon that of the amygdaloidal 

 cavities of the rock. The smallest of these are about the size of a pea or a hazel-nut, while 

 the largest are of considerable dimensions. The weight of an amygdale depends not only 

 on its size but also on the size of the central cavity. The heaviest known is from Brazil and 

 weighs about 40 hundredweights. 



The localities at which amygdale-agate is found are very numerous, but at only a 

 few does it occur in sufficient quantity and suitable quality for ornamental purposes. 



At one time the most important occurrence was in the district of the Nahe, a 

 tributary of the Rhine, in what is now the Oldenburg principality of Birkenfeld, and 

 in the neighbouring portions of Prussia. A portion of this district was formerly 

 included in the Rhenish Palatinate, and for this reason the Palatinate or Zweibriicken 

 are sometimes given as the localities for these agates even now. Melaphyre and 

 amygdaloidal rocks are distributed very widely in this region, and almost everywhere 

 these contain agate, though not always of the best quality. Very fine material is obtained 

 from the Galgenberg, near Idar, and from the Struth, near Oberstein, both localities being 

 situated in Birkenfeld, the latter on the Nahe and the former close to it in the small 

 side valley of the Idarbach ; also from the Rosengarten on the Weisselstein, near 

 St. Wendel, in Prussian territory. The agate of this region has been systematically 

 collected for centuries, and is cut and polished in the numerous lapidary works established 

 there, especially at Oberstein and Idar, which even now turn out a supply sufficient for the 

 whole world. 



Other European localities though numerous are unimportant. The mineral occurs 

 in amygdaloidal rock at several places in northern Bohemia ; for example, on the 

 Jeschkenberg near Fried stein, in the Kosakow mountains near Semil, in the Tabor and 

 Morzinow mountains near Lomnitz, and in the Lewin mountains near Neu-Paka. At these 

 localities many of the amygdales have been weathered out of the rock and lie loose in the 

 ground, or are found as pebbles in the rivers, for example, in the Iser and Elbe. Besides 

 agate, carnelian and other varieties of chalcedony, as well as jasper, are found here and cut 

 at the lapidary works at Turnau, Liebenau, and Gablonz. 



Mention should also be made of the so-called Scotch pebbles, very pretty agates, which 

 occur in considerable abundance at Montrose in Forfarshire, in Perthshire, and at many 

 other localities in Scotland. 



The occurrence of agate in countries other than Europe, especially in South America 

 and to a certain extent also in India, is far more important. From the former country 

 since the exhaustion of the German localities the lapidary works at Idar and Oberstein have 

 obtained an abundant supply of excellent material. 



In South America the principal localities for agate are situated in the Brazilian 

 State of Rio Grande do Sul and the neighbouring country of Uruguay, the material from 

 this region being termed, irrespective of locality, Brazilian agate. In association with it are 

 found the crystallised varieties of quartz already mentioned, namely, amethyst and citrine, 

 and several varieties of chalcedony other than agate, especially carnelian. In this region, 

 just as on the Nahe, melaphyres and amygdaloidal rocks extend over a wide area, and here 

 also agates and other quartz minerals have been formed in their cavities. Very frequently 

 the amygdales have been weathered out of their mother-rock, which is usually completely 

 decomposed and altered to a red or brown, highly ferruginous clay. When this clay has been 

 washed away by rains the agate amygdales are left behind loose on the ground, and they 

 are often found, too, as rounded pebbles in the alluvial deposits of streams and rivers. The 

 amygdales are usually shaped like a cake, flat on one side and rounded on the other, and are 



