PENROSE.] 
PHOSPHORITES OF NASSAU. 
47 
The phosphatic deposits vary from six inches to six feet in thick- 
ness and seem to attain their greatest continuity in a belt running in a 
northeast and southwest direction, thinning out gradually at both ex- 
tremities. They seem to occur only with the limestone, and are no 
longer found when that rock disappears. This would seem to indicate 
that they depend on the limestone for their origin. 
Fig. 22. Section at Cubach, Nassau, Prussia. After D. C. Davies : Geological Magazine, London, 18G8. 
A, clay; B, phosphate of lime ; C, manganese; D, dolomite. 
The phosphorite is found in a great variety of forms. It is generally 
massive, fibrous, earthy, porous, jasper-like, kidney-shaped, stalactitic, 
or nodular. Occasionally there are found in it minute crystals of 
apatite (Davies). Sometimes, also, it occurs as an incrustation, and it 
is then known as staffelite, from its abundance near the town of Staffel. 
Fig. 23. Section at Staffel, Nassau, Prussia. After D. C. Davies : Geological Magazine, London, 1S68. 
A, dolomite; B, clay; C, phosphate of lime. 
This mineral is, generally, white, yellow, green, or brown in color, and 
occasionally translucent. The other varieties are of almost all colors, 
white, yellow, red, gray, blue, green, brown, or black. Occasionally a 
brecciated variety is found, but the larger part of the deposit is of the 
massive kind. 1 The hardness varies from 1 to 5. With the phosphor- 
ite occasionally occur deposits of crystalline hematite and manganese 
ore. These minerals are most common on the outside edges of the 
phosphate-bearing area, but are also found with it in the same deposit. 
The amount of phosphate of lime in the phosphorite is very variable, 
averaging from 60 to 92 per cent, (see analyses). It is generally richest 
when associated with the least hematite and manganese and, when free 
from the former mineral, it makes an excellent superphosphate. Among 
the other minerals associated with this deposit are wavellite, calcite, 
quartz, wollastonite, jasper, and chalcedony. 
J Dr.. C. U. Shepard, jr., MS. 
(521) 
