228 REPORTS ON INVESTIGATIONS AND PROJECTS. 



tion occurs below this temperature the true wollastonite found every- 

 where in nature is reproduced. Furthermore, if crystallization occurs 

 at higher temperatures and the silicate appears in the pseudo form, 

 upon cooling down again it goes over into true wollastonite below this 

 inversion temperature under favorable conditions. This offers rather 

 striking incidental evidence of the formation temperature of portions 

 of the earth' s crust. The appearance of one form of mineral at certain 

 high temperatures and of another form at lower temperatures without 

 change in the chemical composition, together with the fact that only 

 the lower form is found in natural rocks, leads at once to the con- 

 clusion that portions, at least, of the rock formations in which this 

 mineral occurs must have solidified at temperatures below this limit. 



In the study of the feldspars we were able to show that the partic- 

 ular formation known to the mineralogist as the zonal structure can 

 only occur between certain definite limits of temperature. Thus we 

 have twice obtained trustworthy evidence of the temperatures of 

 natural rock formation. 



The work on wollastonite is practically finished and will be ready 

 for publication during the present year. 



While the component wollastonite was being studied work was 

 also begun on ferrous silicate, another essential component of the 

 pyroxene group and one which has proved very difficult to manip- 

 ulate, owing to its excessive oxidation. This mineral has never 

 been successfully prepared in any high degree of purity, and the 

 problem therefore necessarily involves the development of new chen#- 

 ical processes for the preparation of ferrous carbonate as well as 

 the determination of the conditions of equilibrium between ferrous 

 carbonate, ferrous oxide, and the oxides of carbon for the range 

 of temperature involved — a problem which has a direct bearing on 

 the terrestrial conditions of formation. Furthermore, in so far as 

 the chemical processes involve the reduction of common ferric oxide 

 to ferrous oxide and metallic iron, reactions of vital interest to 

 metallurgists are involved, which are important enough to carry 

 through very carefully and to incorporate in an independent publi- 

 cation. 



As these two efforts to produce the necessary components of the 

 pyroxenes in sufficient purity have progressed, a good deal of work 

 of a preliminary character has been done upon some simple combi- 

 nations of lime and silica and of magnesia and silica, in so far as 

 these are within the reach of that portion of the plant which is in 

 operation. It will hardly be wise to offer premature conclusions 

 upon this work, but the progress which has been made allows us to 



