Calcium Metasilicate. 91 



of it, in a few instances,* have been obtained by intention 

 from artifical magmas, usually without any clear insight into 

 the causes of its formation. Hussakf obtained it as one of 

 the products from a mixture of silicates and borates of calcium 

 and sodium ; Doelter^: from a magma made of lime and silica 

 with fluorides of calcium and sodium. Methods of this kind 

 will evidently yield mixtures more or less complex of which 

 wollastonite is - only one constituent and in which, the experi- 

 menter is confined entirely to optical methods for the exami- 

 nation and identification of the mineral. 



In connection with an extended study of the pyroxenes, it 

 was our purpose to prepare wollastonite, determine its proper- 

 ties, and discover, if possible, its relation to the artificial form. 



Suspecting that temperature was the determining factor,§ we 

 first prepared a glass of the composition CaSi0 3 , and by heat- 

 ing this at a temperature of 800° to 1000° succeeded in get- 

 ting true wollastonite in pure condition and in portions of 

 50 grams at a time. The glass, to be sure, is a little difficult 

 to prepare on account of the strong tendency of the liquid to 

 crystallize. Although once we obtained 100 grams of it by 

 simply cooling in the furnace where it was melted, it almost 

 always crystallizes prematurely when thus treated. The safest 

 way is to melt smaller portions and then chill suddenly in cold 

 water. 



For the preparation of the glass, we used the purest quartz 

 and calcium carbonate obtainable. The latter contained only a 

 few hundredths of a per cent of alkali and magnesium, the 

 quartz, about two-tenths of one per cent of total impurities, 

 chiefly oxide of iron. The ingredients were weighed in exact 

 proportions and melted in a platinum crucible. It requires 

 over 1500° to melt this mixture, a temperature readily reached 

 by a Fletcher gas furnace. || When the contents of this cruci- 

 ble are quite fluid, the crucible is seized with tongs and 

 plunged into cold, w r ater, care being taken not to agitate the 

 liquid silicate. In this way, one obtains a brilliant colorless 

 glass. Frequently a portion will crystallize in spite of the 

 efforts of the operator, but if the quantity is small and not too 

 much scattered, it can be separated mechanically from the glass 

 with little trouble. The glass needs now only to be heated in a 

 platinum crucible over the flame of a Bunsen burner, when it 

 crystallizes directly and quite rapidly to wollastonite. 



* Morozewicz, N. Jahrb. f. Min. 1894, ii, 223. Vogt, Die Silikatschmel- 

 zlosungen i, p. 45. 



f Hussak, Zeitschr. fur Kryst. und Min., xvii, 101. 



JDoelter, Tschermak's Mitt. Petr. Mitth., x, 83, 1888. 



§ Doelter has also expressed this view. N. Jahrb. f. Min. Referate, 1886, 

 i, 123. 



|| 41a— Buffalo Dental Mfg. Co. 



