Miurral Synthesis. 167 



thin plates, wollastonite and diopside, were common products, 

 while in magnesian iron glass diopside was formed. 



Having passed in review the methods of crystallizing 

 amorphous substances, we will now consider that group of 

 methods in which the chemical reaction or formation takes 

 place at the same time as the crystallization. 



Again, under the head of sublimation, minerals may be 

 formed by the action of one gas upon another, as in the 

 mixing of oxygen and hydrogen sulphide to form sulphur. 

 Or there may be an action of a gas or gases on molten or 

 solid bodies. In this case the temperature used may be much 

 reduced. Deville formed corundum by action of water vapor 

 on the chloride of alumina. Margottet, through the influence 

 of sulphur vapor on native silver, in presence of a stream 

 of nitrogen, formed argentite. 



The temperatures in these experiments were high, being 

 above the fusing point of the substance. The sulphides and 

 sulpho-salts were formed through action, hydrogen sulphide 

 on the chloride, oxide, or carbonate, of the mineral sought ; 

 for example, pyrite was formed by action of hydrogen sulphide 

 on iron oxide, at a temperature not far above the ordinary. 

 At a temperature of 400 degrees, millerite, covelline, cup- 

 ferite, were formed. Minerals ma} be formed ar.d crystallized 

 from a fused state, by melting together the constitut nts. By 

 mixing silicic acid, iron oxide, alumina and carbonates of 

 alkaline earths, then fusing and cooling, are formed leucite, 

 augite, nepheline, anorthite, cordierite, at temperatures of 

 1,200 to 1,500 degrees. 



These high temperatures are troublesome, so means are 

 sought to avoid them. Certain fluxes are thus found useful ; 

 these are of two kinds : one in which the flux exerts no 

 chemical influence on the mixture, as in case of garnet, 

 formed by adding to the constituents some easily -fused 

 chlorine metal, as manganese or calcium chloride. This 

 method was used by Hautefeuille to form leucite. Or, again, 

 the flux may exert some chemical action, as in the experi- 

 ments of Gorgeu, who fused calcium fluoride and chloride 

 with silica, obtaining augite and wollastonite. Micas, also, 

 were formed by melting together silicic acid, alumina, and 

 fluorides of sodium, calcium, and magnesium. 



