PBNRosE.1 PHOSPHORITES OF SOUTHWESTERN FRANCE. 49 
thin out very rapidly at a short distance from the surface. They often, 
however, continue for some distance longitudinally. Thus, at Pendar<§| 
the surface of the phosphate lead is three to ten yards wide and has 
been followed in a straight line for 100 yards. Any sudden turn or curve 
in the fissure is, according to Mr. Rey-Lescure, 1 almost sure to make the 
lead thin and poor. The richest leads are those which run in a straight 
line and have walls which are smooth and tend toward a vertical po- 
sition. According to Mr. Daubree, 2 the fissures seem to follow certain 
definite directions. Thus, at Pendare and Mas-Merlin, they run ENK. 
andWSW. At the same time there is another series of leads running at 
right angles to these. The phosphatic material of the leads running in 
different directions is of very different character, as will be hereafter 
shown. 
The phosphorite occurs in a great number of forms. Sometimes it 
has a rounded, concentric, and radiated structure; at others it occurs 
in nodular and mammillated masses. Often it is found in agate-like 
zones, forming twenty to thirty layers in a thickness of a centimeter. 
Sometimes it occurs as geodes, 3 and at other times it is found in fibrous 
masses, very much resembling aragouite. The phosphorite varies very 
much in hardness, compactness, aud general appearance. The purest 
form is as hard -as apatite, has a resinous or subvitreous luster and 
a yellowish-brown color. Sometimes the color is of a light blue, pos- 
sibly due to the presence of phosphate of iron. The impure varie- 
ties are white, yellow, or red, and are often soft and earthy. The 
phosphorite which occurs in the form of nodules is often hollow in 
the interior, containing loose stones in the cavities (Daubree). The 
whole mass is mixed with siliceous pebbles, clay (more or' less ferrugi- 
nous), loose blocks of calcareous rock, and pisolites of iron, all solidified 
into a mass varying very much in compactness and generally contain- 
ing numerous cracks and cavities. Often pyrolusite is associated with 
the phosphorite, occurring in thin layers or in the form of dendrites. 
The presence of iodides has been detected, in which respect it resembles 
the phosphorite of Amberg in Bavaria. Minute quantities of bromides 
are also found. The presence of pisolites of iron is most frequent near 
beds of iron ore ; and the iron, according to Bey-Lescure, 4 probably has 
been derived from such beds. 
Mr. Trutat has found that in the leads which run EKE. and WSW. 
the phosphorite is compact, vitreous, agate-like, and, rarely, geodic. 
In the leads at right angles to these the mass of phosphatic material 
consists apparently of geodes filled with carbonate of lime or ferrugi- 
nous clay. The geodes are, however, generally broken and in fragments, 
so that their contents cannot be observed. The leads of the first variety 
1 Bull. Soc. gdologique France, 3d series, vol. 3, 1875, p. 398. 
2 Comptes rendus Acad, sci., Paris, vol. 73, 1871. 
3 Mr. Leymerie: Note sur les phosphorites du Quercy, Toulouse, 187-3. 
4 Bull. Soc. ge'ologique France, 3d series, vol. 3, 1875, 
Bull. 46 4 (523) 
