71 Buddington — Natural and Synthetic Melilites. 



and reactions with impurities may explain the changes 

 observed. 



When the sarcolite is held for 40 hours at 1150°, how- 

 ever, it breaks down and all the grains are locally so full 

 of minute, much higher refracting dots that they appear 

 cloudy and brownish in color. Some of the grains invert 

 to material of negative optica] character, whereas others 

 remain unaltered except for numerous minute dots. 

 Some of the inverted grains show a trace of glass. A few 

 grains of the sarcolite contain small pseudo-cubes as the 

 result of recrystallization. Many of the clouded brown- 

 ish grains have a clear border which has higher indices 

 than the original sarcolite. Similarly, when held for 2 

 hours at 1170°, the sarcolite grains are partly changed 

 to minute pseudo-cubes of higher indices of refraction 

 with here and there traces of glass. Positive evidence of 

 inversion without trace of melting is lacking and the 

 experiments do not prove whether such may or may not 

 take place, as the rate of reaction may be so slow that a 

 longer time interval or the presence of a mineralizer 

 would be necessary. 



Fuggerite. 



Weinschenk 19 has described a mineral near Lake Selle 

 in the Monzonithal which resembles in some of its proper- 

 ties some of the gehlenite-akermanite series. It occurs 

 in limestone at the contact with monzonite and is in thick 

 four-sided tabular crystals, probably tetragonal. The 

 color is light apple green and the density is 3.18. Indices 

 of refraction for yellow light are essentially the same : 

 nu = n e = 1.691, with anomalous interference colors. It 

 is decomposed by dilute acids with separation of pulveru- 

 lent silica. 



A chemical analysis of the material was made by 

 E. Mayr, and this on recalculation gives about 40 percent 

 2CaO.Al 2 3 .Si0 9 , 35 percent 2CaO.Mg0.2Si0 2 , 10 percent 

 3CaO.Fe 2 03.3Si6 2 , 10 percent 3CaO.Al 2 3 .3Si0 2 , and 5 

 percent 3Na 2 O.Al 2 3 .3Si0 2 . An artificial mixture of 

 this composition crystallized just below the solidus 

 (1345° ± 10°) had the following indices for the crystals: 



19 E. Weinschenk, Z. Kryst., 27, 577, 1896. 



