the whole vitreous mass appears to be the chief difficulty in its manufacture.
The
dexterity requisite to accomplish this must be very difficult to
attain, for the profits realized from the manufacture of aventurine are
remarkably large. According to its quality, the artificial gem sells
for $5 to $15 the pound, while the raw materials that enter into the
composition of a pound of it are certainly not worth a quarter-dollar.
French chemists—M. Hautefeuille in i860, and
M. Pelouze in 1865—have published processes by which productions have
been obtained equal to that of Venice, and, in the latter case, perhaps
superior.
The
new aventurine of M. Pelouze has a beautiful lustre, and a hardness
exceeding that of glass and ordinary aventurine. It is obtained by
melting together 250 parts sand, 100 parts carbonate of soda, 50 parts
carbonate of lime, and 40 parts bichromate of potassium. It will be
seen that by this formula the spangles with a basis of copper are
replaced by spangles with a basis of chrome.
FALSE PEARLS.
False
pearls are little hollow spheres of glass covered internally with a
coating imitating the orient of natural pearls. Their fabrication com-
