52 
DEPOSITS OF PHOSPHATE OF LIME. 
BULL. 46. 
when the exports ceased. The best deposits had given out and the oth- 
ers contained so much iron and alumina that the material was very unde- 
sirable as a source of superphosphate. For several years, from 1870 to 
1875, an average of 20,000 tons per annum was exported. 1 Some of the 
mines are still worked, but the phosphate is used only in a raw state 
and for local purposes. 
Soon after mining had begun in this region, Guillier estimated that 
the total contents of all the mines would not exceed 100,000 tons. This 
estimate was much too small, but it serves to show that the deposit is 
a very limited one. The phosphate was formerly collected in loose 
bowlders from the fields for the purpose of building walls. At the 
Pearl mine, near Cajarc, the phosphorite crops out at the surface. 1 At 
the depth of 75 feet the lead becomes very thin and uncertain. The 
mass of the phosphorite is, in some places, 10 feet thick, but ordinarily 
it consists of several more or less parallel bauds, which end abruptly. 
One of the largest mines is at Larnagol, in the department of Lot. 
It is situated on the summit of an Oxfordian plateau over a thousand 
feet high. The first quality rock is cleaned by hammer and hand, and 
the second quality in a simple horizontal washer, driven by steam. The 
phosphorite contains both chlorine and fluorine, but in much smaller 
quantities than exist in apatite. As has been said before, it also contains 
iodine, and in some specimens traces ot bromine have been detected. 
Table of analyses of phosphorites from southwestern France. 
[I. Analyses by Bobierre.] 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
VIII. 
1.00 
38.00 
51.47 
9. o3 
4.70 
32.94 
12.70 
36.48 
• 
12.06 
35.84 
3.00 
36.80 
1.00 
37. 10 
1.40 
37.00 
51.50 
10.10 
0.93 
38.32 
48.92 
11.83 
Phosphoric acid 
Total lime 
Water volatilized at red 
beat, fluorine, chlo- 
rine, carbonic acid, and 
oxides of iron and 
manganese 
Lime in excess of phos- 
phoric acid, and com- 
bined with carbonic 
acid, fluorine, and 
chlorine 
100. 00 
C.87 
100. 00 
8.10 
100. 00 
3.94 
Dr. C. U. Shepard, jr., MS. 
(526) 
