. I
don't really know that much about Trancas Coconuts. But it seems that a
small percentage of any Trancas Coconuts contain black and white agate,
others are just quartz geodes and chalcedony. Those Trancas "Coconuts"
provided a clue that any type of "Coconuts" may be forms of fully-expanded
"thundereggs". The thundereggs have rhyolitic shells, and it happens that
those Trancas "Coconuts" have such shells too as well as other characteristics
of thundereggs.
Rhyolite shell attached to the agate is an evidence
that the Trancas Geodes are acutally fully-expanded thundereggs.
