253 



Tlie specific gravity at 25,r (\ was: r^,, = 3.204 ± 0,003 for I lie 

 natural, not yet melted compound; after soiiditication of the molteu 

 mass, one obtains, after slowly cooling, a colourless, finely crystal- 

 lized mass, whose density differs considerably from the original mineral; 

 it is: r/40= 2,385 at 25°,1 C. 



The refi-active indices of the molten and solidified substance are 

 considerably different from those of the original mineral. While for 

 the unmelted substance we found respectively: y/^ = J, 053 ± 0,003; 

 ^i^ = 1.669 ± 0,003; and «, i^z 1,672 d= 0.003 '). for the solidified 

 mass we found an extremely feeble birefringence of about 0,001, 

 and a mean refractive index of: «/;= 1,518. The crystalpieces showed 

 an irregular extinction, evidently by very coni[)licated intergrowth 

 of several individuals. 



On rapidly cooling, an isotropous glass was obtained, with a 

 refractive index of Wu = J,517 ± 0,001, being about the same as 

 for the crystallized mass. The specific gravity was at 25°, 2 C. : 

 (/,o = 2,388 ± 0,003. When heated during a longer time at 1300° C, 

 it becomes crystalline; even at lower temperatures the glass gets 

 soon opaque and like [)orcelain by devitrification ; but glass and 

 crystalline product obtained from it, evidently do not differ in iheir 

 properties to any appreciable amount. 



II. Kunzite of the Sahatany -valley on Madagascar. Big, clear and 

 completely transparent crystals; they are dichroitic and tinged with 

 a pale rose hue. Locally the environing rock-material is again 

 discernible, as a rusty coloured, finely divided substance. The crystals 

 were carefully cleaned from it; then they were ground and sieved, 

 after which the investigation proceeded in the usual manner. 



As a mean value for a greater number of determinations, we 

 found the meltingpoint at: 14683 + 5 M.V. ; as the correction of 

 the thermoelement was — 8 M.V. at this temperature, we can adopt 

 the value 14675 M.V. of the E.M.F. of the thermoelement at the 

 meltingpoint, corresponding with: 1428" C. (G. Th.); in this case 

 the meltingpoint is also veiy sharp. 



Evidently this kunzite differs only slightly from the pi'eceding 

 mineral of Rincon. With respect to its chemical composition, we 

 have some data, given by Lacroix'-), who investigated colourless. 



1) In a liquid of' «u = 1,670, composed of melhylene-iodide and nionobromo- 

 naphlaline, the crystalpowder showed a very beaulil'ul reddish-violet colour, just as 

 some of Christiansen's "monochromes". The same phenomenon was observed for 

 the glass and the (3-modification of artificial spodumene. 



2) A. Lacroix, Mineralogie de la France et ses Colonies, IV, 775, (1910). 



