Buddington — Natural and Synthetic Melilites. 83 



give an anomalous berlin-blue interference color for day- 

 light. Surrounding the cores are zones showing yellow- 

 ish-brown interference colors grading outward into 

 material with normal yellow interference colors. The 

 index of refraction of the isotropic cores is about 1.654 

 and the indices of the material exhibiting the maximum 

 interference colors are nj> = 1.666 and n E = 1.661 with a 

 birefringence of about 0.005-0.006. Peg structure is 

 conspicuous. 



The material is so intimately associated with nephel- 

 ite and pyroxene that it was necessary to grind it to a 

 fineness sufficient to pass a 150 mesh screen. Bromof orm 

 was then used to separate the lighter constituents, Klein's 

 solution to effect a first separation of the melilite from 

 the pyroxene, and an electro-magnet to complete the puri- 

 fication. The melilite after this treatment was found, 

 when examined under the microscope, to contain about 

 4 percent pyroxene and 2 percent nephelite. 



Table XXX. 

 Capo di Bove Melilite. 



I II 



Si0 2 40.56 40.03 



A1,0 3 6.18 5.66 



Fe,0 3 7.44 7.76 



Feb 51 .40 



MnO none none 



MgO 9.53 9.43 



CaO 31.07 32.17 



Na.,0 2.96 2.83 



K 2 1.76 1.72 



Ti0 2 none none 



100.01 100.00 



I. Analysis of Capo di Bove melilite with 2 percent nephelite and 4 

 percent pyroxene. Washington, analyst. 



II. Analysis recalculated for pure melilite. 



Only a small amount of material was obtained from 

 a large amount of the granular nodule. A chemical 

 analysis was made of this by Dr. Washington. Owing 

 to the small quantity of material available, only 0.2936 

 gramin all, water was not determined. In Table XXX 

 are given the original analysis and the analysis recalcu- 

 lated to eliminate the effect of the impurity of 2 percent 



