i68 Cinciruiali Society of Natural History. 



Another method of mineral formation is through a chem- 

 ical reaction in the wet way or by solution agencies. The 

 action of hydrogen sulphide on metallic chlorides and 

 oxides in solution forms sulphides. vSo lead, iron, or silver 

 chlorides, in solution of sodium carbonate, in an atmosphere 

 of hydrogen sulphide, yield crystals of the sulphides. This 

 method was used very successfully Vjy Weinschenck. These 

 minerals were formed by the action of gases on solutions. 

 Other minerals have been formed by the influence of a solu- 

 tion on a solid body. 



If sodium sulphide is brought in contact with an oxide of 

 some metal under ordinary pressure and .slightly-raised tem- 

 perature, good sulphide crystals of that metal are formed. 

 Doelter and Bischoff used this method to form hematite, 

 pyrite and galena. This action of one solution on another at 

 ordinary temperature is a fruitful source of new minerals. If 

 sodium sulphate and lead chloride be brought together in 

 solution, fine crystals of anglesite are formed. This method 

 was used by Drevermann and Becquerel. Using the last 

 method with high temperatures and pressures malachite was 

 formed by influence of sodium carbonate on copper sulphate. 



A few minerals form amorphous precipitates at ordinary 

 temperature, but when this is raised, the substance crystal- 

 lizes: as, magnetite in mixture of carbonate of sodium and 

 chlorides of iron. Friedel and Sarasin formed orthoclase at 

 550 degrees by action of alumina silicate on the calcium sili- 

 cate. Other minerals thus formed were, albite, quartz, tri- 

 dymite, pyroxene, and wollastonite. 



Pressure alone has been found effective in formation of a 

 limited number of minerals. vSpring formed chalcocite from 

 copper filings and powdered sulphur under a pressure of 5,000 

 atmospheres. 



Electrolysis has been successfully used, and copper, gold, 

 lead, and the like, have been produced. One mineral, which 

 has long withstood attempts at its formation, has been artifi- 

 cially reproduced within the last few years. 



A description of this experiment will illustrate, in a general 

 way, the manner of conducting a synthetical mineral repro- 

 duction. 



