THE GEOLOGIST. 
67 
showing, at the same time, the results obtained, some years ago, by M. 
Moberg, in the analysis of some emeralds from Finland : — 
Emeralds from Mexico (M. Lcwy). Emeralds from Finland (M. Moberg). 
Silica . . . 67-9 67-359 
Alumina . . 17-9 lC-46.5 
Glucina . . 12-4 12747 
Magnesia . . 0 9 — 
Oxide of iron — 1'49 
Soda ... 0-7 ....... . — 
Titanic acid . traces 0-28 
Both these analyses show that the emerald contains 1 atom of alumina, 
1 atom of glucina, and four atoms of silica. In that of M. Lewy 
slight traces of chromic oxide were weighed with the magnesia, and 
probably some titanic acid with the alumina. The green colour of the 
emerald is darker in those specimens which furnish to analysis most 
organic matter; it is completely destroyed by heat, the stone becoming 
white and opaque. 
On the communication of these results to the Academy, M. 
Bousingault observed that he also, in former days, had visited the 
Muso mine, and that he had picked out of the strata in which the 
emeralds are found, pieces of gypsum of a beautiful green colour, 
resembling that of the emerald. He had no doubt, from M. Lewy's 
observations, that the green colouring with which the gypsum was 
impregnated was identical with that just discovered by M. Lewy in 
emeralds. 
M. Daubree has furnished us with some new and interesting details 
concerning the artificial production of minerals. By a close observation 
of the methods employed by nature, and a certain intrepidity in the 
laboratory, this enthusiastic geologist has had the good fortune to 
produce some crystallized specimens of minerals which have never before 
been purposely formed or accidentally found in scoriffi. He formerly 
observed in the mineral springs at Plombieres, the waters of which 
contain silicate of potash and soda, and have a temperature of + 70° 
Centigrade, the formation of certain well-known silicates and other 
minerals usually found in the veins of eruptive or primitive rocks. 
Most of these have been formed, since the time of the Romans, in the 
orifices of the mineral springs in question. An old Roman tap in 
bronze was found covered with a crust of sulphide of copper which, 
