Wright — Three Contact Minerals. 551 



such as to simulate very closely crossed dispersion of the mono- 

 clinic system. 



Before the blowpipe spurrite shows strong calcium flame 

 reaction, loses its glassy lustre, becomes white and porcelain- 

 like but does not fuse even in thin splinters. 



Spurrite effervesces readily with weak hydrochloric acid, 

 dissolves completely and gelatinizes thoroughly. The chemical 

 analysis was made on carefully selected material. 



The agreement of the analyzed material with the formula 

 2Ca 2 Si0 4 .CaC0 3 is remarkably close and in view of the purity 

 of the material analyzed can leave no doubt that spurrite is a 

 compound of the above formula. 



The specific gravity at 25° was determined with pycno- 



meter, both in xylene and in water, and the following results 



obtained : 



Spec. gr. at 25° in xylene = 3-013 



cc cc i 3*014 



water = 



Average spec. gr. at 25° = 3-014 



Spurrite occurs in the hand specimens either in pure, unal- 

 tered state, except for minute inclusions of magnetite, or 

 together with yellow garnet, calcite and gehlenite. Its weather- 

 ing products consist chiefly of carbonates in microscopic aggre- 

 gates, which appear first along cracks and cleavage |)lanes in 

 the altering mineral. 



Through the courtesy of Mr. E. S. Shepherd of the Geo- 

 physical Laboratory, several experiments were made to repro- 

 duce spurrite artificially by heating ten per cent solutions of 

 sodium chloride with pure Ca 2 Si0 4 and CaC0 3 in finely divided 

 state and in different proportions in silver-lined steel bombs 

 from 6 to 9 days at temperatures of 350° to 400°. Although 

 minute, well-shaped crystals were obtained in many of the 

 preparations with refractive indices a and 7, practically identi- 

 cal with those of spurrite, the symmetry was orthorhombic 

 and therefore not that of spurrite. Synthetic experiments on 

 this compound are still in progress. 



This mineral is named in honor of Mr. J. E. Spun* of New 

 York, who collected the original material and who has done 

 much to further existing knowledge of ore deposits and their 

 accompanying minerals. 



Hillebr -andite* 



Hillebrandite, unlike spurrite and gehlenite, is distinctly a 

 fibrous mineral and occurs in aggregates often as radial spheru- 



* Type specimens from the 8th level of the Terneras Mine, Velardena, 

 Durango, Mexico. 



