)0 
DEPOSITS OF PHOSPHATE OF LIME. [bull. 46. 
ually blend into one another, thus often rendering it uncertain to which 
class a special deposit should be referred. The classification given be- 
low is based mainly on the chemical composition of the deposits. These 
are grouped under two principal headiugs, namely, mineral phosphates 
and roclc phosphates. 1 The former includes all deposits of phosphate 
of lime which, besides having the other properties inherent in a true 
mineral, have a definite chemical composition or at least show a strong 
tendency toward such properties and composition. The latter includes 
thosedeposits which, *having no definite chemical composition and lack- 
ing the homogeneous nature and other fixed characteristics of a true 
mineral, cannot be classed with mineral phosphates. These two classes 
are aafairi subdivided as follows: 
i »* 
^ Apatites J Fl nor- apatites. 
Mineral phosphates. < l \ Chlor-apatites. 
( Phosphorites, 
f ( Loose nodules. 
j Amorphous nodular phosphates. < Cemented nodules or conglom- 
( erates. 
Rock phosphates, t Phosphatic limestone beds. 
I n \ Soluble guanos. 
Guanos. < T 1 i 
I } Leached guanos. 
[^Bone beds. 
The various phosphate deposits of North and South America, Europe, 
Africa, and other localities will be treated under the different divisions 
of the above classification, each deposit being described under the head- 
ing to which it belongs. Mineral phosphates will be taken up first, and 
then the various representatives of rock phosphates will be described. 
Special attention will be given to the phosphate deposits of the United 
States and Canada, which were visited and studied by the writer. 
MINERAL PHOSPHATES. 
APATITES. 
Apatite is found in both stratified and crystalline rocks, but is much 
more plentiful in the latter, especially in metamorphic limestone, syen- 
ite, garnetiferous, hornblendic, and pyroxenic, gneiss, mica-schist, and 
igneous and volcanic rocks. 
The mineral occurs in both the massive and the crystalline form. It 
belongs to the hexagonal system of crystallization, has a vitreous or 
subresinous luster, is translucent and sometimes transparent, has a 
hardness of 5, a specific gravity of 3.17 to 3.25, is brittle, of a white, yel- 
low, green, or red color, gives off phosphorescent light when heated, 
1 It will be seen that the determination which phospbate shall be classed under 
minerals and which under rocks must in certain cases be somewhat arbitrary, but 
the classification is intended simply as a matter of convenience in describing the 
various deposits, and as such answers its purpose sufficiently well. 
(496) 
