Jan. 15,1917 
Calcium Compounds in Soils 
65 
the greater part of the type. Good crops of cotton, corn, peanuts, and 
cowpeas are secured under proper treatment. 
petrographic examination 
Preliminary to chemical work, the samples were examined under the 
petrographic microscope for the presence or absence of the most impor¬ 
tant calcium-bearing minerals. The minerals sought for and their for¬ 
mulas are as follows: 
Calcite.CaC0 3 . 
Dolomite.(Ca, Mg) C0 3 . 
Hornblende... Chiefly Ca (Mg, Fe) 3 Si 4 0 12 with Na 2 Al 2 Si 4 0 12 and (Mg, Fe) a 
(Al, Fe) 4 Si 2 0 12 . 
Augite.Chiefly CaMgSi 2 0 6 with (Mg, Fe) (Al, Fe) 2 SiO Q and occa¬ 
sionally alkalies. 
Gypsum.CaS0 4 +2H 2 0. 
Apatite.(CaF)Ca 4 (P0 4 ) 3 or (CaCl)Ca 4 (P0 4 ) 3 . 
Plagioclase... . Isomorphous mixtures of NaAlSi 3 O s and CaAlSi 2 0 8 . 
Epidote.HCa 2 (Al, Fe) 3 Si 3 Q 13 . 
Titanite.Ca Ti Si0 5 . 
n ni n hi 
Garnet 
Zoisite 
R 3 . R 2 (Si0 4 ) 3 . R==Ca, Mg, Fe, Mn. 
Ca^AlOH) Al 2 (Si0 4 ) 3 . 
R=A1, Fe, Cr, and 
rarely Ti. 
The results are presented in Table II, in which P indicates that the 
mineral designated is present plentifully (approximately above 5 per 
cent); S that it is present in small quantities (scarcely above 3 per cent); 
VS that it is present in very small quantities (1 per cent or less); and T 
that it is present in traces. In a few instances the examination indicated 
that a mineral was probably present, but its identification was not sat¬ 
isfactory. This is indicated by T?. 
Tabi*E II .—Petrographic analysis of soils for calcium-containing minerals 
Class and No. 
Cal¬ 
cite. 
Dolo¬ 
mite. 
Horn¬ 
blende. 
Augite. 
Gyp¬ 
sum. 
Apa¬ 
tite. 
Plagio- 
cl§se. 
Epi¬ 
dote. 
Tita¬ 
nite. 
Gar¬ 
net. 
Zoisite. 
Class I: 
T 
$ 
T 
s 
s 
s 
s 
•2 
s 
S 
T 
T 
T 
0 . 
A 
s 
T 
T 
T 
T 
4. 
s 
T 
T 
5 . 
6 
T 
s 
T 
s 
T 
s 
s 
s 
7. 
ft 
T? 
vs 
T 
VS 
O. 
VS 
T 
g 
Class II: 
s 
s 
s 
T T 
s 
s 
s 
TO 
s 
T 
T 
T 
T? 
I 3. 
s 
s 
*4 . 
t e 
s 
S 
S 
s 
s 
x 5 . 
s 
s 
S 
S 
T O 
T 
s 
S 
x 7. 
18. 
VS 
VS 
VS 
