108 DEPOSITS OF PHOSPHATE OF LIME. [bull. 46. 
(3) Sables Glauconieux (Chloritic Marl of England). 
(4) Gaize (Upper Greensand of England). 
(5) Gault Argileux (Ganlt of England). 
(6) Sable Vert (Lower Greensand). 
The above section can be seen in many places in the western part of 
the provinces of Ardennes and Meuse. 
The nodule beds in the Upper and Lower Greensand resemble, in 
many respects, the corresponding beds in England. The Lower Green- 
sand has a very variable thickness, sometimes running out almost 
entirely, and at others attaining a depth of 50 feet. It is at the base 
of this mass of sandy clay, colored sometimes by grains of glauco- 
nite, that the Lower Greensand phosphate bed occurs. 1 The nodules 
are rounded, worn, and mixed with many fossils and shell casts. They 
vary from the size of a nut to that of a man's fist. They are of a brown 
color, and are generally of a lighter hue on the surface than in the cen- 
ter. Sometimes the nodules occur loose in the sand and at others, as at 
Clermont and Varennes, they are cemented into a conglomerate. There 
are in the bed numerous shark teeth, shells, remains of crustaceans, and 
other fossils. The nodules often contain grains of quartz and greensand, 
veins or crystals of pyrite, gypsum, and sometimes of galena. There 
are also often associated with them concretions of pyrite, crystals of 
gypsum, and balls of ferruginous clay. 
The French nodules resemble the English in being of a variable con- 
sistency, sometimes being very compact and glassy in appearance, and 
at others being so siliceous that they often, as at Beurey. look like 
grains of sand cemented by a little phosphate. It has already been 
shown that the composition of such nodules, at least so far as the rela- 
tive amounts of silica and carbonate of lime are concerned, depends 
largely on the character of the water bottom from which the nodules 
were formed. 
The nodule bed of the French Lower Greensand is very continuous 
and rarely runs out, 1 though it varies considerably in thickness, rang- 
ing from two to nine inches, and averaging about seven inches. 2 There 
are also nodules, more or less phosphatic, scattered through the overly- 
ing Lower Greensand, as well as through the Gault, but they are not in 
sufficient quantities to be of any commercial importance. The nodules 
and shell casts of the Gault are much more homogeneous and compact 
in their composition than those of the Lower Greensand. 3 
The next phosphate bed, in an ascending series, comes in the Upper 
x Mr. Nivoit: Assoc, franc, avanc. sci., 1875. 
2 The nodules contain 8.80 to 50.54 per cent, phosphate of lime and average 39 per 
cent. 
3 It will be seen that there is only one regular bed of nodules in the French Lower 
Greensand, while in the English formation of the same horizon there are three beds, 
which, however, often run into each other and form one stratum. 
(582) 
