Usually marketed as polish flint, it's a really spectacular material. It takes one hell of a high polish too, and the darker bands are a bit translucent. Other locales produce banded flint but I've never seen any like the Polish material.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Do you happen to have any specific information on this formation? I presume voids in limestone filled by siliceous H2O.....but ending up with chert, not agate? That's................unexpected, no?
Alas, I'm afraid it's actually pretty typical to get chert rather than agate in that context. There's some debate over the exact mechanisms involved as I understand it, but chalk and limestone are the typical hosts for flint/chert nodules. The patterning is in all likelihood a spectacular example of liesegang banding developed during or after the initial nodule formation.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Thanks. I just put a $9 bid on the slab. Yep, it's cracked and not even close to the awesomeness of Norman Mahan's slab......but I am merely a minion in his shadow.
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