322 C. F. de Lander o — Pink Grossularite from Mexico. 



with the rose-colored crystals, that he proposed to visit the 

 locality ; this he accomplished in the early part of January 

 of this year, and succeeded in obtaining excellent specimens of 

 both pink and colorless grossularite. On his return from his 

 trip, he gave me a number of crystals, and since the material 

 was very pure and well suited for chemical work, I decided to 

 analyze it. This I have done in my laboratory, with the assis- 

 tance of my colleague Prof. B. Prieto. 



AYe selected for the analysis, small, clean, almost transparent 

 fragments of rose- colored crystals. The specific gravity was 

 found, by pycnometer to be 3-516 at 19*8° C. The qualitative 

 analysis proved the presence of silica, alumina, lime, magnesia^ 

 and traces of ferric oxide and manganese. Manganese, though 

 probably the coloring matter, is present in so minute quantity, 

 that its reaction with the borax glass could not be obtained, not 

 even by using a fragment of saltpeter to oxydize the glass. 

 Its presence was however ascertained by fusing the powdered 

 mineral with sodium carbonate, a greenish mass being obtained ; 

 this was dissolved in water, with the addition of pure nitric 

 acid, and the clear liquid poured over lead peroxide; after a 

 little time the liquor became pale amethyst-colored. 



For quantitative analysis 0*870 grams of very pure carefully 

 powdered material were fused with 3 grams of the usual mix- 

 ture of dry carbonates of potash and soda, in a platinum cru- 

 cible, over the flame of a gasolene vapor laboratory lamp 

 (Danglers) : the mass obtained was dissolved slowly, in very 

 dilute hydrochloric acid, and the silica, alumina, iron, lime and 

 magnesia were determined in the usual manner. The amount 

 of the original mineral that was not attacked by the alkaline 

 carbonates was ascertained by treatment of the weighed silica, 

 with amnionic fluoride, weighing the residue left, and approxi- 

 mate calculation of the corresponding weight of the mineral- 



The results obtained were the following : 



Per cent. Atomic Ratio. 



4064 5892=310 



21-48 18-13 / 

 1-57 086 ) 



35-38 54-98 f 



0-75 162 S - yb 



trace 

 0-17 



Si0 2 





0-3535 



A1 2 3 





0-1868 



Fe 2 O s 





00131 



CaO 





0.3078 



MgO 





0-0065 



MnO.BaO 





trace 



Unattacked m: 



ineral 



0-0015 





0-8698 



?he atomic 



ratio for ! 



99-99 



Si0 2 , P 2 3 and RO is very nearly 3 : 

 1 : 3, the normal ratio for the minerals belonging to the garnet 

 group. The formula for the analyzed grossularite, may be 

 written: [Ca, Mg] a [Al 3 , FeJ Si 3 12 . 



