Buddington — Natural and Synthetic MeUIites. 75 



n Q = 1.658 and n £ = 1.654, tetragonal system. Crystals 

 formed at 1150 ~ give the same results. It forms a 

 complete solid solution with a melting interval extend- 

 ing from the solidns at 1345° ± 10° to the liqnidns at 

 1423° ± 10°. 



The optical properties of the mineral and of artificial 

 crystals equivalent in composition bnt formed at about 

 1345 \ therefore, do not agree by a wide margin. The 

 difference is far greater than the limits of error involved. 

 The synthetic preparation, therefore, is a polymorphic 

 form involving the same compounds as the mineral 

 fuggerite. 



Many specimens labeled " fuggerite " were obtained 

 by the writer from dealers and museums in the United 

 States, but all were too completely replaced by grossular- 

 ite or were too much altered to be satisfactory for experi- 

 mentation. One specimen alone still showed a minute 

 core of the original material, only partially replaced by 

 garnet. Its indices were similar to those given by Wein- 

 schenk and it showed conspicuous anomalous interference 

 colors. Such garnet pseudomorphs were described by 

 TTeinschenk in his original paper. 



HmiBOLDTILITE. 



The term melilite was originally (1796) applied to the 

 reddish-brown to yellow crystals found in the leucito- 

 phyre at Capo di Bove, Italy, in allusion to the honey 

 yellow color. The name humboldtilite was subsequently 

 (1882) given to the white to greenish crystals of similar 

 crystallographic habit found in the metamorphosed blocks 

 of limestone at Vesuvius. As a result of a study of the 

 chemical and crystallographic characters of these two 

 minerals by Des Cloizeaux and Damour (1843) the min- 

 eral humboldtilite was classified as melilite. Mierisch, 20 

 however, has given sufficient data as to differences in 

 manner of occurrence, crystallographic habit, color, min- 

 eral association, and cleavage between the original meli- 

 lite of Capo di Bove and humboldtilite of Vesuvius to 

 warrant the retention of the latter name to designate in 

 general a series of minerals of the melilite group similar 



20 Tscherm. Mitth., N. F., pp. 149-153, 1887. 



