PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 60. 



been extensively investigated by the geophysical laboratory of the 

 Carnegie Institution of Washington, and their results have, in the 

 main, confirmed Schaller's theory as to the constitution of the group 

 and the composition of the end members. A discrepancy in nomen- 

 clature has arisen, however, which is very confusing. This is due 

 to the fact that the men working on the synthetic compounds of this 

 group have disregarded the name velardenite and have transferred 

 the name gehlenite to this compound. Until some explanation is 

 advanced to justify the deviation from the nomenclature of Schaller, 

 to whom we are indebted for the correct interpretation of the melilite 

 group, natural minerals approaching the pure end member 2CaO. 

 AljOg.SiOg may correctly be called velardeiiites. 



COMPOSITION OP THE GARNET. 



A small amount of a concentrate, consisting largely of the garnet 

 which occurs associated with the velardenite, was isolated with heavy 

 solutions. The portion was small, and in addition to the garnet 

 contained also spinel, which is almost identical with the garnet in 

 specific gravity. One portion only was available, and the state of 

 oxidation of the iron was not determined. It is below assumed to 

 be entirely in the ferric state. An analysis of this small portion 

 of material gave the following composition and ratios : 



Analysis and ratios of garnet {loith spinel). 



Constituent. 



SiC. 

 FcaO 



Ai,o; 



Cab.' 

 MgO. 



Per cent. 



.32. 66 

 24.15 



5.95 

 35. 51 



2.59 



Ratios. 



0. 5416 

 .1512 

 .0582 

 .6331 

 .0642 



54.16 

 20.94 



69.73 



0. 90X3 

 1.04X1 



1.16X3 



The ratios are not satisfactorily close to whole numbers, thus 

 indicating a considerable admixture of spinel. Assuming the 

 greater part of the magnesia and alumina to be present in this form, 

 it is evident that this yellow-green garnet is very largely composed 

 of the lime-ferric iron molecule andradite. 



LOCALITY AND OCCURRENCE. 



The locality for the material is not known more definitely than 

 simply Tulare County, California, and no information regarding the 

 occurrence is available other than that furnished by the specimens 

 themselves. It seems most probable that the velardenite and asso- 

 ciated minerals are here, as in Mexico, products of the contact meta- 

 morphism of limestone. 



