Mineral Synthesis. 



59 



of this influence of method on crystal form is shown in rutile. (See 

 figure I.) When this mineral is crystallized from a hydrochloric acid 

 solution fine needles are formed. If produced by the decomposition 

 of a titanate through quartz, octagonal prisms result ; while a fusion of 

 amorphous titanic acid in the presence of a fluorsilicate of potash 

 produces tabular crystals. 



In a number of other cases different methods of formation pro- 

 duce the same forms, so pyrite always is formed in cubes. 



It is now proposed to describe some of the experiments in the 

 reproduction of a number of the more important minerals. The most 

 widely distributed type, which is to be found in nearly every locality 

 is quartz. Very few of its many varieties have as yet been formed in 

 the laboratories. The elongated prismatic type terminated by the 

 double pyramid and tridymite alone have been formed. The pris- 

 matic variety was first formed in 1845, by Schafhautl, who heated in a 

 Papin furnace for ten days, gelatinous silica recently precipitated. 

 The silica was dissolved and the solution evaporated, and on examin- 

 ing the white powder under the microscope small hexagonal bipyra- 

 midal quartz crystals were seen. 



Daubree noted that the same product resulted from the attack of 

 heated water on glass in a closed vessel. When this action was con- 

 tinued for many weeks at a temperature of 320 degrees, the glass was 

 transformed into a mass of kaolin leaves, and on the surface of each 

 a lens disclosed the prisms and pyramids of quartz. These minute 

 crystals belonged to the two types of right and left handed forms, and 

 they showed striations on the prism faces just as on natural crystals. 

 Small chalcedony spherulites were also formed. 



Another very important group of minerals in the formation of 

 crystalline rocks is the feldspar family. On account of this importance 

 numerous attempts were made to reproduce them but for a long time 

 without success. Leonhard, in 1858, says of these attempts : "The 

 chemists have not succeeded in reproducing feldspar. Mitscherlich 

 attempted to obtain it by the fusion of its elements and always obtained 

 a vitreous mass with no trace of crystalline structure, and so concludes 

 that minerals containing potash and aluminum cannot be reproduced 

 in crystalline form. Before fusion they pass from the solid state to 

 the viscous." 



In 18 10, the accidental formation of orthoclase was noted in a 



