70 Buddington — Natural and Synthetic Melilites. 



completely melted and quenched to form glass. This 

 glass was then recrystallized at 1450° and the resulting 

 crystals had the same indices as the original material. 



California Gehlenites. — A gehlenite from Crestmore, 

 near Riverside, California, has been described by W. F. 

 Foshag. 15 It occurs associated with spurrite and other 

 minerals. It is rather striking that such a rare mineral 

 as spurrite should occur associated with the relatively 

 rare mineral gehlenite at two such widely separated 

 localities. A specimen of the gehlenite loaned by the 

 U. S. National Museum (No. 87275) had the following 

 indices : % = 1.662 ± 0.003, n £ = 1.658 ± 0.003. 



A specimen of gehlenite from Tulare County, Califor- 

 nia, also loaned by the U. S. National Museum, had the 

 following indices: n a =1.660 ± 0.003, m =1.657 ±0.003. 

 This material was associated with garnet (index 1.813 ± 

 0.006), magnetite, and pyroxene, and had a density of 

 about 3.02. It has been analyzed by E. V. Shannon, and 

 the recalculated analysis shows roughly about 66 percent 

 gehlenite, 28 percent akermanite, and 6 percent ferric and 

 ferrous compounds. A comparison of its properties 

 with those of artificial gehlenite having the same ratio 

 of gehlenite to akermanite, but free of iron compounds, 

 is given in Table XX. The agreement is very close. 



The analysis by Shannon, reduced to 100, stated in 

 terms of its constituent molecules and compared with the 

 calculated molecules in a mixture of assumed components 

 most closely approximating the natural mineral in com- 

 position is given in Table XXI. 



Table XXI. 

 Gehlenite from Tulare County, California. 



Original Analysis Calculated Differ- Mixture 



analysis reduced. Mol. molecules ence weight percent. 



Si0 2 27.88 27.75 4602 4814 +212 66 2CaO.Al 2 3 .Si0 2 



Al 2 O s 25.52 25.40 2490 2400 — 90 28 2CaO.MgO.2SiO, 



Fe 2 3 1.59 1.58 99 88 —11 4.5 3CaO.Fe,0 3 .3Si6 2 



FeO 43 .43 60 49 —11 1.5 2CaO.Fe0.2Si0 2 



MgO 4.18 4.17 1042 1026 — 16 



CaO 40.86 40.67 7250 7214 —36 



H„0+ 30 



H 2 0— 04 



100.80 100.00 



15 Am. Mineralogist, 5, 80-81, 1920. 



