SILICA. 
311 
That the composition of this mineral does not differ essentially from that of some varieties 
of pyroxene, and of metalloidal diallage, will be evident from the following statement: 
Pyroxene, by H. Rose. 
Silica,. 54.08 
Lime, . 23.47 
Magnesia,... 11.49 
Protoxide of iron,. 10.02 
Protoxide of manganese,. 0.61 
Metalloidal Diallage, by Kohler. 
Silica,. 51.34 
Lime, . 18.28 
Magnesia,.. 15.69 
Protoxide of iron and manganese, . 8.23 
Alumina,. 4.39 
Water, . 2.11 
The true Labrador hypersthene contains, it will be observed, a much smaller proportion of 
lime (see page 310). 
The Warwickite of Shepard, which closely resembles hypersthene in its external charac¬ 
ters, has been found to contain a large proportion of titanium, and will be therefore described 
under that metal. 
SCHILLER SPAR. 
[From the German, signifying chatoyant spar.] 
Schiller Spar. Thomson. — Schiller Spar. Phillips and Shepard. — Diallage. Hauij and Cleveland. — Diato- 
mous Schiller Spar. Jameson. — Diatomcr Schiller Spar. Mohs. 
Description. Colour dark green, almost blackish green. Streak yellowish grey. It occurs 
in broad foliated masses, which cleave in two directions, and apparently have the primary 
form of a rhombohedron. One of the cleavages is easily obtained, and has a metallic pearly 
lustre and a pinchbeck brown colour. The laminm are slightly curved. Fracture uneven, 
splintery. Lustre metallic pearly on the faces of cleavage. Opaque, and yields to the knife. 
Sectile. Hardness from 3.5 to 4.0. Specific gravity 3.65. Thin fragments, treated by the 
blowpipe, are merely rounded on the edges, but become of the same brown colour as when 
they have been long exposed to the air, and are attracted by the magnet; with borax it is fu¬ 
sible, though with difficulty, and the glass, when cold, has a greenish colour. 
Composition. Silica 43.90, magnesia 25.86, protoxide of iron and chromium 13.02, pro¬ 
toxide of manganese 0.53, lime 2.64, alumina 1.28, water 12.43 {Kohler). 
Geological Situation. This mineral was generally supposed to be found in serpentine ; 
but it appears, from the analysis of Kohler, that the stone in which it occurs is identical in 
composition with that of the schiller spar. 
fusible by the blowpipe, and according to the analysis of Mr. H. Seybert, contains silica 52.17, lime 20.00, magnesia 11.33, 
alumina 4.00, deutoxide of iron 10.73, water 1.00. Cleaveland’s Mineralogy, Appendix. 
