255 



25°,1 C. In botli cases (lie mean refmclive index for sodinmlight 

 was: Uu = \, bis + 0,001. From the moUen mass tlierefore no other 

 phase is deposited than the mentioned |3-moditi{*ation. 



The fig. 5, 6. and 7 may give an impression of the manner, in 

 which the transformation of the a-, into the /^-modification gradnally 

 occurs. In fig. 5 the original kunzite of JlJadagascar is photographed 

 between crossed nicols, when heated only during 2 hours at 975° C, 

 and showing no trace yet of the /?-form ; in tig. 7 tlie same iieating, 

 but prolonged to 15 hours, has led to complete transformation of the 

 crystals into the y3-form. The fig. 6 represents the crystals, after 8 

 hours heating at 975° C. ; they show a partial transformation, and 

 the gradually occurring differentiation of the originally homogeneous 

 crystals into an aggregation of the felty needles of the /?-modification. 



III. Greenish-yellow Kunzite of Minas Geraes, Brasil. 



This kunzite appears also in the form of large, very transparent 

 crystals, having a pale greenish or yellowish hue. This colour is 

 caused by a content of FeO, wdiich in melting the mineral, is con- 

 verted into: Fe^O^; thus the solidified mass being always tinged 

 with a reddish-brown colour. The analysis of this mineral ^) gave 

 the following data : 



SiO, : 63,3-64,37„ CaO -. 0,2-0,7 '/, 



Al^O,: 27,7-27,97„ Na^O: 0,6-1,0 7» 



Li,0,: 6,7- 7,47„ FeO -. 0,7-1,2 7„ 



This kunzite therefore is also relatively close in composition to 

 that of Rincon, approaching in its content of Li^O closer to the 

 theoretical value ; the sum of the principal constituents is 97,7 7(r 



The meltingpoint of this mineral was determined five times; the 

 results were, with thermoelement IV : 



14643 M.V. 

 14646 M.V. 

 14650 M.V. 

 14639 M.V. 

 14646 M.V. 

 Mean value: 14645 M.V. ; 

 after correction : 14637 M.V. (G. Th.) 

 The meltingpoint, reduced on the nitrogengasthermoineter. lies 

 thus at 142')° C, i.e. about 3" C. lower than for the kunzite oï Rincon. 

 The specific gravity of the substance before melting, w^as deter- 

 mined at 25°,1 C. to be: (Z^o:^ 3,262; the data, given in literature 

 for the specific gravity of natural crystals, vary between 3,16 and 



1) G. HiNTZE, Handbuch der Mineralogie. 



