Chap. XIX.] 
MANGANESE IN LATERITE. 
889 
ore is a variety of psilomelane its composition may lie anywhere between 
certain fairly wide limits ; for it seems that a piece of psilomelane may 
contain as much as 20 per cent, of iron without showing any visible 
difference from an ore containing only per cent, of iron and a corres- 
pondingly greater amount of manganese. This leads to a great vari- 
ability in the composition of the ores despatched, unless they are 
carefully assayed, and judiciously blended or mixed so as to keep 
the output up to a certain standard. The average percentage of 
iron in these ores is considerably higher than in the Central Provinces 
ores, with a correspondingly lower figure for the manganese. On the other 
hand, the lateritic ores, as a consequence of their mode of formation, 
are usually much lower in silica than the Central Provinces ores. 
The phosphorus also seems to be consistently lower. These features of 
the lateritic ores are well shown by the following figures, which should 
be compared with the figures for the Central Provinces and Vizagapatam 
ores given on pages 510 to 513 : — 
Table 24. 
Analyses of lateritic ores. 
Shirnoga.2 
Belgaiini.l 
Higher grade 
ores. 
Lower grade 
ores. 
Sandur.l 
Jraugaiiese 
31-2 —60-8 
44 —56 
30 —38 
39-47 —54-39 
Iron 
01 —18-4 
2 —10 
10 —20 
5-38 —19-40 
Silica 
0 0 — 2-5 
1 — 3 
2 — 0 
0-43 — 1-00 
Phosphorus . 
0 01 —0-12 
0-015 — 0 060 
0-01 — O'G 
0-016— 0-(33 
1 From figmcs supplied by Mr. C. Aul)ert. 
2 From figures supplied l)y C. Fawcitt. 
