414 On the Chemical Composition of Phospliatic Minerals 
in irregular masses, exhibiting a variety of colours, which give it 
a peculiar mottled appearance. 
The richest varieties have a botrjoidal structure, and are 
nearly white or light yellow ; and equally rich are the deposits, 
which, like some of those found at StafFel, are covered with a 
light green crystalline semi-transparent incrustation. 
Lahn phosphates of a low quality are more or less contami- 
nated with clay-ironstone, clay, phosphate of iron and alumina, 
carbonate of lime, dolomite or manganese, and iron ores, or 
mixtures of all these impurities. 
Unfortunately the richer qualities are becoming more and 
more scarce from year to year ; and during the last two or three 
years the quality of German phosphate has deteriorated to a 
degree which has almost put a stop to the importation of Nassau 
phosphate into England. 
After these general remarks on German, Nassau, or Lahn 
phosphate, as it is called indiscriminately in England, I wish to 
direct attention more especially to the chemical composition of 
a number of representative specimens and cargo-samples which 
have passed through my hands during the last ten years. In 
the first place, I subjoin detailed analyses of three selected 
specimens which I picked up at Staffel, on the occasion of a 
visit of inspection to the phosphate mines in the valley of the 
Lahn. 
Detailed Composition of Three Specimens of Bich Nassau 
Phosphate (Staffelite). 
No. 1. 
No. 2. 
No. 3. 
•65 
40-56 
56^29 
1-21 
•97| 
"-32 
-25 
38-12 
53-92 
-b3{ 
-691 
3-16r 
2-75 
•09 
•09 
-98 
36-19 
49-44 
-96 
3- 07 
2-88 
1-87 
4- 61 
100-00 
100-00 
100-00 
88-54 
83^21 
6-25 
79-01 
4-25 
The analyses of No. 1 and No. 2 were made with selected 
pieces of the light green crystalline semi-transparent incrus- 
