Petrological Abstracts and Reviews 



CHARLES H. BEHRE, JR. 



Ferguson, J. B., and Merwin, H. E. "The Melting Points of 

 Christobalite and Tridymite," Amer. Jour. Sci., XL VI (1918), 

 417-26, figs. 2. 

 A description of experimental methods employed in testing the melting 

 points of these two minerals. A high-temperature furnace, built on the cas- 

 cade principle, and capable of maintaining a temperature of 1700° for several 

 hours, is described. By means of this furnace quartz has been inverted directly 

 through dry heat alone. The melting point of tridymite has been determined 

 (for the first time) as 16 70° ±10° C; that of christobalite has been redeter- 

 mined; it is 1 7 10° ± 10° C. Christobalite is stable at higher temperatures than 

 tridymite as determined earlier by Fenner. 



Ferguson, J. B., and Merwin, H. E. "Wollastonite (CaO.Si03) 



and Related Solid Solutions in the Ternary System Lime- 



Magnesia-Silica," Amer. Jour. .Sci., XL VIII (1919), 165-89, 



figs. 8. 



A further experimental study of the liquidus curves for the system of these 



three oxides, though not completely quantitative, yet confirms the earlier work 



with the same system, demonstrates the existence of solid solutions of diopside 



up to the amount of 16 per cent in pseudowoUastonite and diopside, and of 



akermanite in woUastonite and pseudowoUastonite. A new compound — 



5 Ca0.2Mg0.6Si02 — is reported. The paper contains also a fairly complete 



discussion of resxilts obtained in the curves derived, and photographs of the 



solidus-liquidus concentration-temperature models. 



Ferguson, J. B., and Merwin, H. E. "The Ternary System CaO. 

 MgO.SiO^," Amer. Jour. Sci., XL VIII (1919), 82-123, figs. 19. 

 This is the most comphcated system of any that can be constructed of three 

 of the four oxides, CaO, MgO, AI2O3, and Si02. Forsterite, diopside, enstatite, 

 tridymite, cristobalite, lime, magnesia, pseudowoUastonite, and two compounds 

 of the three oxides were obtained. Solid solutions of five types were also 

 recognized in crystaUine form; these included clino-enstatite-diopside solutions, 

 pseudowoUastonite solutions of varying composition, woUastonite solutions, 

 solutions of an unnamed compound of the three oxides, and menticellite solu- 



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