They were called "Mexican Coconuts"
because of their nearly perfect spherical shapes, and they tend to be either
filled with white to gray agate or lined with quartz crystals, hence "geode".
The colors of agate are typically white to gray, sometimes with light bluish
hue with some coming with very strong shadowing effects. The most prized
of any Mexcian Coconuts would be those with deep purple amethyst geode
centers as well as those agates in any colors beside white, gray and bleu
colors. I have seen some with yellow agate with bits of red. Even they
have been produced in adundance, very small percentage of them actually
would produce any with solid quality agate. I cut a crater full of Mexican
Cococnuts(55) and got only four "Coconuts" containing solid agates. Rest
are just low quality geodes, solid quartz cores, and solid geothite &
calcite cores. Some "Coconuts" contained weird sagenite-like structures.
I have obtained some clues that
the "Mexican Coconuts" may have been a form of fully expanded thundereggs
resulting from the rhyolitic & pertilic lava flowing over something
very wet. Something wet (aquifer?) under the rhyolitic & pertilitic
lava flow provided an adundant source of water vapor that would fully expand
the cavities within cristobalite nodules just like the thundereggs in balloon-like
manner. I wouldn't be surprised that the pertile lava flow was so enriched
in water that it decomposed into clay layers very quickly providing the
source of minerals that would fill the cavities of "Mexican Coconuts".
I am managed to find one "Mexican Coconut" with rhyolite attached to it
which is a good evidence, and it has been donated to Paul "Geodekid" Calburn
for purpose of science studies on the formation of thundereggs.
