910 
to be possible; these erystallisation-temperatures were however 
always 260 to 700 M.V. dower than the melting temperatures; also 
in this ease the said method can never lead to the knowledge of 
the equilibrium-temperatures. 
The meltingpoint of pure rhodonite thus may be fixed at 1273° 
+1°C.; evidently there are two transition-temperatures at resp. 
1208° C. and 1120° C. Furthermore the melting-points of all natural 
rhodonites appear to be lower: for the rhodonite from Auvergne it 
is almost equal to that of the artificial product, and the same can 
be said of the first transition-point : - 
Meltingpoint : Transitionpoint : 
Auvergne : 1270° 1206°. 
Sweden : 1266° — 
Radau-Tal: 1258° —= 
Franklin N.J.: 1221° dln Op 
The optical properties of the solidified products with the artificial 
_ and natural rhodonites were also identical with each other: 
n, = 1,739 + 0.003 and n, = 1,783 + 0.003 ; the birefringence: is 
only feeble, about: 0,007. For the glass we found: n= 1,700. 
The beautiful crystals are parallelogrammatically shaped, with an 
obtuse angle of about 107°, and an extinction-angle of 14°. There 
ean be no doubt about cdentity of both kinds of crystals. For the 
natural rhodonites some data are reviewed here : 
Rhodonite from | Rhodonite from | Rhodonite from ; 5 
Radau-Tal Auvergne | Franklin, N. J. | Rhodonite fi rom Langbin 
Natural After being | Natural | After being | Natural After being | Natural | After being 
Crystal | melted Crystal melted | Crystal | melted | Crystal melted 
| | | 
in air 
| | | | 
n= 1.122 | my —=1.712 | my =1.136 | my = 1.783 | nj —1.129 | my = 1.725 | my —=1.102 | my = 1.700 
My = 1.709 | my = 1.705 | my = 1.729 | my = 1.722 | m= 1.722 | my = 1.716 | my = 1.693 | m= 1.693 
¢=0.013 | 20.007 | *7=0.007| o=0.011 | o=0.007 | ¢=0.009 | ¢=0.009 | «=0.007 
| | in nitrogen | 
— | -- | 2, = 1.729 | — — — — 
| Ny = 1.722 
|| soy 10 007 
| 
