A quartz crystal included by hairy (tremolite?) and cookeite spheres.... it almost looks like a fish laied eggs in this thing.
It seems that the first generation (which now constitutes the internal phantom) was included heavily with tremolite. Cookeite spheres deposited on its surface, and then a second generation of quartz grew over all that, creating what you see here.
A beautiful and unusual example of rare Japanese material.