Pyrolusite Concretions — SHERMAN, et al. 
123 
less water of hydration or a greater purity in 
the minerals making up the concretions. It 
would appear that the composition of the pyro- 
lusite concretions is not affected by the type of 
deposition since there is greater variation be- 
tween individual concretions within the type 
than between the types. 
The nature of the deposition of the Mn0 2 
around certain specific nuclei rules out the sub- 
mergence hypothesis of origin. The formation 
of the concretions has been the result of soil 
weathering since they have been precipitated 
in those soils which have developed under alter- 
nating wet and dry conditions. The alternating 
wet and dry condition of the soil is essential 
in the development of concretions of pyrolusite 
and ferruginous-pyrolusite concretions since it 
provides the conditions for the solution, leach- 
ing, oxidation, and precipitation of the man- 
ganese which are necessary for the process. 
Kelley (1912) has pointed out that pyrolusite 
concretions are not found in soils which re- 
ceived sufficient rainfall to keep the soil in a 
moist condition throughout the year. 
SUMMARY 
Pyrolusite concretions are found in small 
areas within the manganiferous soils, the red 
soils, of the Hawaiian Islands. These concre- 
tions are found in the soils of the drier regions 
which have definite wet and dry seasons. The 
origin of the pyrolusite concretions in these soils 
has been the subject of some speculation. Two 
hypotheses have been proposed: namely, that 
the concretions were developed during a period 
of submergence of the islands, and that they 
have developed as a result of the weathering of 
lavas at higher elevations and the subsequent 
leaching of the manganese to lower elevations 
where it has been precipitated. 
Pyrolusite concretions have been found which 
have developed around the roots of a shrub. An 
appreciable portion of the concretions found in 
Hawaiian soils has been developed by the depo- 
sition of Mn0 2 around the roots of plants. Fur- 
ther studies suggest that the spherically shaped 
concretions have been formed by the deposition 
of Mn0 2 around very small nuclei. The irregu- 
larly shaped concretions have been deposited 
in cracks in the soil, earthworm burrows, and 
larger openings in the soil. 
The concretions have been analyzed; their 
Mn0 2 content varies from 23.1 to 44.2 per cent. 
REFERENCES 
Kelley, W. P. 1909. Pineapple soils. Hawaii 
Agr. Expt. St a., Ann. Rpt. 1909: 58-63. 
1910. Pineapple investigations. Hawaii 
Agr. Expt. Sta., Ann. Rpt. 1910: 14-16, 
41-43,45-50. 
1912. The junction and distribution of 
manganese in plants and soils. Hawaii Agr. 
Expt. Sta., Bui. 26: 42-56. 
Murray, J., and A. F. Renard. 1891. Deep sea 
deposits — Scientific results of the voyage of 
H.M.S. Challenger, 1873-76. London. Pp. 
337-412. [Quoted by W. P. Kelley, 1912.} 
Piper, C. S. 1944. Soil and plant analysis. 368 
pp. Interscience Pub. Co., New York. 
