In the laterite at the
surface and in the horizon near it, numerous blackish brown pisolite
with diameters of several mm to about 1.5cm are contained. Some of
the pisolites can be divided into crust and core from their internal
structure, which is similar to that of Mn nodule on ocean floor. In
the crust, several light and dark stripes are produced in a
concentric circle. The minerals comprising these stripes are
considered to be very fine particles irregularly intermixed, but two
minerals 4.7 A manganite and goethite, can be detected clearly. At
time, from the core to the crust, along with the major constituent,
Fe and Mn, Co, Ni and Cr are found at higher concentrations than in
the surrounding laterite, and some correlation between Mn and Co, or
regular distribution of some other elements are observed.