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Ch. 18: Quartz, Amethyst, Citrine

Ch. 18: Quartz, Amethyst, Citrine Page of 401 Ch. 18: Quartz, Amethyst, Citrine Text size:minus plus Restore normal size   Mail page  Print this page
       
     
 
THE QUARTZ FAMILY.
357
  
 
 
  
 
Oberstein and Idar, in Germany, are the chief centres of
the agate industry. Those cut at these places were formerly
obtained, to a great extent, from the hills bordering the River
Nahe, but more recently they are brought from other countries, those from South America constituting a large part of
the agates of commerce. The process, briefly described, of coloring this gem artificially, is as follows : The stone is first
washed and dried, then laid in honey and water, and placed in
a heated oven, care being taken that the water does not boil.
This treatment is continued from fourteen to twenty-one days,
after which the agate is removed from the honey and washed,
then soaked in sulphuric acid, in a covered vessel overspread
with hot ashes and burning coals. After being subjected to
this roasting process a sufficient length of time, it is removed,
washed, and dried. By this complicated treatment, the syrup
in which it is immersed is absorbed by the more porous layers,
then carbonized by the action of the acid, which forms the
dark-colored varieties, but the red specimens are obtained by
boiling the gems in a solution of protosulphate of iron, and
then exposing them to heat. If laid in oil several hours, the
agates acquire great brilliancy. The so-called Brazilian carnelians are prepared in a similar manner at the celebrated works
of Oberstein. The jeweller of to-day, says Mr. King, can see
no difference between the German silex, artificially stained,
and the precious Indian agate, though the art student, and, it
may be added, the practical mineralogist, are enabled at once
to detect and appreciate the distinction.
This gem often exhibits some curious features of Nature's
fantastic handiwork, as when it presents striking likenesses
of certain persons, such as are seen in a specimen in the British
Museum, with a portrait resembling the poet Chaucer ; one in
the Florence gallery, with a Cupid running ; one in the Straw-
  
 
 
  
       
Ch. 18: Quartz, Amethyst, Citrine Page of 401 Ch. 18: Quartz, Amethyst, Citrine
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