[HARRINGTON ] MINERALOGICAL CHEMISTRY 15 
The decomposition of the sulphide was in each case effected by heating 
the finely powdered mineral to 200° along with a ten per cent solution 
of copper sulphate in a sealed tube for six hours. At ordinary temper- 
ature and pressure the copper solution had little effect on either mineral, 
and the same was true when the solution was boiled. Under pressure, 
however, the decomposition was found to be complete, the sulphur com- 
bining with the copper to form copper sulphide and the iron passing 
into solution as sulphate. 
In no branch of mineralogical chemistry has greater advance been 
made of late years than in the artificial production of minerals. With the 
exception of a few isolated attempts to produce artificial minerals, scien- 
tific work in this direction may be said to belong entirely to the present 
half of our century, and to have originated in the experiments of Ebel- 
men, who was for some time director of the porcelain manufactory at 
Sévres, and who succeeded in producing the ruby, spinel and other 
minerals by artificial processes. 
While much has been accomplished in other countries, more especially 
in Germany, the chief founders of the synthetic method in mineralogical 
chemistry have been Frenchmen. As evidence of this we have but to 
mention such names as those of Durocher, Daubrée, Senarmont, Debray, 
H. Saint-Claire Deville, Becquerel, Hautefeuille, Fremy, Fouqué, Michel- 
Levy, Friedel, Sarasin and Bourgeois. Several of these investigators are 
still the active exponents of what has been justly termed the French 
School in synthetic mineralogy.’ 
The methods employed in the synthetic production of minerals are 
varied in character, and in some cases are designed to imitate the pro- 
cesses supposed to be carried out in nature. The object, however, is to 
produce not simply a definite chemical compound, but as far as possible 
one exhibiting the crystalline form and physical characters belonging to 
the natural mineral. Some of the methods accordingly are designed to 
convert amorphous into crystalline bodies, while the object of others is 
the direct production of a crystalline mineral. 
By way of illustration a few of the methods employ a and the results 
obtained may be given. The conversion of amorphous into crystalline 
bodies is in some cases brought about by heating in gases which have no 
apparent chemical action upon them. Zine sulphide, for example, becomes 
crystalline when heated in an atmosphere of nitrogen, and amorphous 
stannic oxide may be converted into beautifully crystalline cassiterite by 
heating in hydrochloric acid gas. In other cases the gas (or vapour) 
plays an obvious part in a chemical change, as when galena is produced 
by the action of hydrogen sulphide upon lead chloride, 
PbCI, + HS = PbS + 2HCl, 

1 See MeGow an’s translation of E. von Mey er’s “History of Chemistry,” 1891. p. 
475. 
