Comments on: Stone-cutter finds fossil whale in marble slabs

By: TJ

TJ — Tue, 15 Nov 2011 00:26:16 +0000

Some may think Casey’s question esoteric, but it is not. I thought in my head as I read the article, jeez, I’m going to have to modify my thinking on fossils in marble…especially cause I collect minerals, fossils and am a jewelry maker. I’m constantly asked to identify things for people, and was mentally modifying the mental file on marble… The points on degrees of alteration and the loose relationship between dimension-stone names and geological nomenclature which rarely coincide are well taken.
Go to home depot or a bead store and look at the “flexibility” in naming granites, calcium carbs, jaspers, oh, and my personal fave, Onyx!

By: Casey

Casey — Wed, 09 Nov 2011 18:42:32 +0000

Zak – I did read the first two sentences…and the rest of the article. That still doesn’t answer the question of how the fossils made it through the metamorphism. As Callan and Steve said, the quarryman’s definition of “marble” (and hence “marbilized”) might be different from the geologic definition of marble. Also as Callan pointed out, there’s different degrees of marbleization (or recrystallization) that can occur during the formation of marble. So the whole issue for me comes back to the geologic setting of the formation of the marble. If the parent limestone was extremely hydrothermally altered, I wouldn’t expect to see fossils as intact as those found in this sample.
So long story short, “marbilized limeston” isn’t my answer. Or at least my complete answer.

By: Zack

Zack — Wed, 09 Nov 2011 16:53:22 +0000

Casey-

Did you read the first two sentences of the article?

“In July 2002, an Italian man named Mr Francioni found something strange. Francioni owns a marble-cutting company in the Tuscan town of Pietrasanta, and he had just acquired a block of Egyptian marbleized limestone.”

marbleized limestone. There is your answer.

By: Casey

Casey — Tue, 08 Nov 2011 21:54:56 +0000

Callan and Steve – I didn’t even think of that as an explanation for “marble”. That would make a lot of sense. I guess the jury’s out until/if we find out if it was “marble” or marble. Ed – any chance you have access to the full paper and if so does it mention specifically what’s going on with the rocks?

By: Ed Yong

Ed Yong — Tue, 08 Nov 2011 20:17:31 +0000

Thanks for the rich comment thread folks. Just a quick note to say that I recently switched to a system where people can post freely if they’ve done so before; otherwise, it joins a moderation queue. So it may take a brief while for things to appear.

By: Callan Bentley

Callan Bentley — Tue, 08 Nov 2011 17:10:21 +0000

Casey: There are degrees of recrystallization that a limestone can undergo to make a “marble.” Perhaps a small amount of recrystallization is the case in these rocks, or perhaps they are simply limestones that have been marketed by stone merchants as “marble.” After all, “marble” is one of the two words in the stone cutter’s vocabulary. The other is “granite.” 99% of the time, these terms are used in a much looser sense than their strict, specific geological definitions.

By: Casey

Casey — Tue, 08 Nov 2011 16:51:37 +0000

Dan – I remember hearing stories about how, during road building in the Valley and Ridge province in West Virginia, they used to find huge fossil trees and complete skeletons and just dump them in the crusher because no one wanted them. I’m SURE that’s no the only time that’s happened.

By: Daniel J. Andrews

Daniel J. Andrews — Tue, 08 Nov 2011 16:38:32 +0000

Hmm. I like Casey’s point. Now I’m curious about that too.

Wonder how many really good fossils have been broken up or discarded never to be found again over the centuries of quarrying, road building, etc.

By: Steve

Steve — Tue, 08 Nov 2011 16:35:06 +0000

Casey, You are correct from a geologist’s perspective. Marble is a metamorphic rock and the recrystallization often destroys or at least distorts fossil — depending on the degree of metamorphism. However, stonecutters often refer to any calcium carbonate rock (e.g., limestone, dolomite, marble) as simply marble — especially if it has veining, swirls, or other textures that make beautiful cut stone. I suspect that in this article, “marble” was used in the stonecutter’s sense.

By: Charlie Petit

Charlie Petit — Tue, 08 Nov 2011 15:33:55 +0000

Casey’s right. One wants to know how unusual marble in particular is as host to fossils and whether, as the host rock is harder than the fossil, or so I gather, how long did it take to separate the two? They use chisels, grinders, both..what? Fascinating story in any case Ed.