414 
Phosphorite in Estremadura. 
iron, partly at least in the state of peroxide, together with one or two per 
cent, of silica, and a large proportion of fluoride of calcium. 
The following are the results of an analysis made of one of the purest 
specimens that could be selected, or, we should rather say, the mean of 
two analyses, in either of which similar quantities taken from the same 
specimen were operated upon, the results of the two agreeing nearly 
together : 
Silica 1-70 
Peroxide of iron . , . . . 3'15 
Fluoride of calcium . . . . . 14*00 
Phosphate of lime . . . . 81'15 
ioo 00 
There was likewise 0*2 per cent, of chlorine, united with calcium, 
present in the mineral. 
The silica and iron are probably accidental ingredients; but the 
fluoride of calcium is so commonly associated with phosphate of lime, 
that it may be regarded as essential to the mineral in question. 
It is known to occur, not only in mineral apatite, but also in a vari- 
able, but generally small proportion, in bones, and the enamel of teeth, 
both fossil and recent;* thus appearing to perform some hitherto unascer- 
tained office in the animal economy, so that a wonderful provision of 
nature seems to be unfolded to us, when we observe, treasured up in the 
older rocks, as if in anticipation of the wants of the future creation, a 
dt5put, not merely of an ingredient, like phosphate of lime, which was 
so requisite for building up all the solid parts of animals, but also, 
in constant association with it, a certain proportion of fluate of lime, 
which appears in like manner to enter into the composition of the same 
fabrics. 
It will be remarked, however, that the per-centage of fluate of lime, 
which we have set down as existing in the mineral, is much larger than 
that present in any other specimen that has before been analysed. 
Thus Gustavus Rose gives the analysis of 7 varieties of apatite, taken 
from different localities, in which the largest proportion of fluoride of 
calcium discovered was 7 "69 per cent., the smallest being only 4 '59. 
We should therefore hsive been reluctant in stating a result so little 
conformable with those of this distinguished chemist, had not there been 
a very near accordance between the results obtained from two specimens 
which were examined ; and also if we had not considered that the varie- 
ties of apatite which Rose analysed were probably all crystallized, whilst 
those of the Spanish phosphorite submitted to analysis were in a compact 
or amorphous condition. 
The remarks just made have reference to the colourless or purer 
variety of the Spanish phosphorite, through which, as already observed, 
are disseminated streaks or thin zones of a dark brown variety. The 
latter was found to owe its colour to peroxide of iron, here present in a 
• See a paper on the occurrence of fluorine in recent a-s well as in fossil 
bones, by Charles Daubeny, M.D., &c., in the Memoirs of the Chemical 
Society, Part 9. 
