908 , 
about 1228° C. Quenching-experiments gave no positive results; a 
single indication was obtained, which could lead to the conelusion, 
that the meltingpoint should lie in de neighbourhood of 12560 M. V. 
i. e. at about 1252° C. The crystallised substance consists of irre- 
gularly shaped, strongly birefringent grains, probably resembling 
those of artificial willemite, which probably is isomorphous with 
the Cd-compound. Both vefractive-indices are greater than 1,739. 
§ 10. Manganese-Metasilicate ; Manganese-Orthosilicate; Rhodonite 
and Tephroite. 
The ortho-, and meta-silicate of manganese were obtained from a 
basie manganese-carbonate, which, as analysis showed, contained 
54,1°/, MnO, and from pure quartz. Because on melting in plati- 
num-crucibles in the open air, always black needles of higher oxides 
were observed, the components were then melted in the FrETCHER- 
furnace in graphite-crucibles, closed with a cover of the same 
material. Certainly a rose coloured product was now obtained; but 
the crucibles burnt very rapidly, and the carbon soiled the silicate 
too much, to continue the experiments any longer in this way. 
Thus the graphite-crucible in the FrLercner-furnace was again re- 
0 
placed by a platinum-crucible, which was tightly closed by a cover 
of graphite, turned on the lathe. In this way we obtained a pure 
rhodonite, or by quenching in cold water, a pink glass, which on 
heating in the Bunsen-flame was again transformed into a red crys- 
talline mass. Analysis gave the following data: 
Crystals : Glass : Calculated : 
SiO, 46.25°/,  46.20°/, 45,95°/, 
MnO 53,8 °/, 53,8 °/,° 54,0 9, 
So the product still contains 0,25 °/, ScO, too much; but it was 
only accidentally possible to approach nearer to the theoretical com- 
position. 
The preparation of the ortho-silicate occurred in quite the same 
way; after twofold correction, the analysis gave: 
Observed : Calculated : 
SiO, 29,60°/, 29,82°/, 
MnO 70,4 */, 70,2 °/, 
The product has a brownish-black colour, and consists of glittering 
erystals, which on grinding give a grey powder. 
Besides the artificial rhodonite: MnSiO,, we also investigated the 
meltingpoints, ete. of a number of natural, very pure and selected 
rhodonites from Radau-Tal, from Franklin N. J., from Auvergne 
