426 On the Chemical Composition of Phosphatic Minerals 
10. Sombrero Phosphate. 
Sombrero rock-phosphate is found on the small uninhabited 
island of Sombrero, one of the group of the Leeward Islands in 
the Caribbean Sea, situated about 60 miles east of the Danish 
West Indian Islands, and the same distance from Guadeloupe. 
This valuable rock-phosphate was noticed in my paper pub- 
lished in 1861, in which a number of detailed analyses of it will 
be found. 
At one time large quantities were imported into England ; but 
at the present time not many cargoes are sent to this country, 
and it is to be feared that the greater portion of the accessible 
rock has been quarried and carried off. 
In 1865 a Company was formed for the purpose of working 
and exporting this phosphatic rock ; but, mainly on account of 
insufficient capital, it failed in 1870. However, the liquidator 
of the Company managed the business of the creditors so favour- 
ably, that in 1871 a new Sombrero Company was constituted, 
with whom rests, at present, the exploration of the phosphate 
still existing on the island. 
At present the rock is worked under the level of the sea at 
much expense, and the exportation is effected under considerable 
disadvantages, for the island is surrounded by coral-reefs, and 
ships are therefore obliged to cast anchor at some distance 
from the island, and to take in their cargo from lighters ; and 
during the stormy season, extending from September to January, 
the shipping has to be suspended altogether. 
The following is the composition of four cargoes imported 
into England in the course of the current year : — 
COMPOSITIOX OF SOMBEEEO PHOSPHATE, 
No. 1. 
No. 2. 
No. 3. 
No. 4. 
Oxide of iron and alumina, &c 
814 
32-82 
45-33 
0-5S 
7-14 
•99 
7-03 , 
1 1-64 : 
I 32-45 
4611 
7 33 
1 4-29 
115 
7-63 
1-49 
31^70 
45-92 
1 7-30 i 
4-87 
1-09 
1 8-92 
31-73 
45 69 
5-99 
7-07 
•60 
100-00 
100 00 
100-00 
100 00 
* Equal to tribasic phosphate of lime .. 
t Equal to carbonate of lime 
71-65 
12-08 
70-84 
16 64 
i 
1 69-20 
j 16-59 
69-27 
13-61 
Tlie Sombrero phosphate of recent importations is a light- 
coloured and tolerably porous material, which is readily ground 
