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POPULAR SCIENCE REVIEW. 
was found near Oberstein in 1 844. The cavities in which the 
larger agates occur, were probably formed by the coalescence of 
several gas bubbles in the original lava. 
Whatever agates are found in this country are comparatively 
small, the finest being the well-known “ Scotch pebbles,” prin- 
cipally from the Perthshire traps. Larger and finer stones are 
found in the melaphyre of Oberstein, especially in a hill known 
as the Galgenberg, or Steinkaulenberg, near Idar, a small town 
about two miles from Oberstein. As the mother-rock decom- 
poses, the imbedded agates fall out, and these accumulating in 
the soil attracted attention at a very early date. It was, in 
fact, this occurrence of agates that led to the systematic quarry- 
ing of the melaphyre, and to the planting of agate-mills in the 
neighbouring valleys. Documentary evidence carries us back 
four centuries, to a.d. 1454 ; but how much earlier the Gralgen- 
berg agates were worked it is difficult to conjecture.* Only, 
however, within the last forty years has the industry been fully 
developed, and this development has unquestionably been due 
to the large supply of fine stones from South America. In fact, 
for many years past the agate-quarries of the Gralgenberg have 
not been worked. The writer of this article visited them about 
ten years ago, under the guidance of an old agate-worker in 
Idar, but found that they had been long deserted. Adits had been 
run into the escarpment of the hill, and the softer parts of the 
melaphyre worked by irregular galleries. Agates, more or less 
perfect, are scattered in all directions over the floor of the 
workings, and may be picked out of the walls and roof; but 
these stones, though pretty enough as specimens, are for the 
most part scarcely worth cutting, consisting, as they generally 
do, of a thin rind of chalcedony, lined with a crop of amethyst 
crystals. A few German agates may, however, be still gathered 
by the poorer workers, though practically the mines have been 
abandoned in favour of the South American stones.f 
It was in 1827 that some Idar agate workers, who had 
emigrated to South America with the view of settling in the 
German colony of St. Leopoldo, observed that the courtyard of 
a country house was paved with pebbles not unlike the familiar 
stones of their own hills. Specimens sent home, when cut, 
polished, and stained, turned out to be beautiful carnelian. 
The fortunate discoverers collected with ease, from the bed of the 
Pio Taquarie in Uruguay, several hundredweight of the loose 
* u Die Halbedelsteine und die Geschichte der Achat-Industrie,” yon G. 
Lange. The writer is much indebted to this work for local and technical 
details. 
t For a description of the quarries as they appeared thirty years ago, see 
Mr. W. J. Hamilton’s paper in “ Quart. Journ. Geol. Soc.,” vol. iv. p. 209. 
