Any of you experts know the answer to this?

[winyan]

Can a fossilized snail shell gradually show opalescent qualities?

win

 

[valeria101]

Snail...terrestrial snail? - the genus would probably not be old enough for such geological transformation. Opalized ammonites are to be found by the truck load and there are enough opalized fossils of, usually, marine shell-building organisms (bivalves, mostly, but not only). There are quite a few types of opalized fossils... what is the object of your Q, exactly ?

 

[winyan]

Hi AnA,

Thanks for responding. Actually someone in Australia asked me the question, I wasn't at all sure of the answer, tried to look it up, without much success, so I thought I'd ask here. Apparently she found one, but wasn't sure if it was unusual or at all valuable, or even if she should keep it.

Thanks!

win

 

[valeria101]

I see... I supose what your friend found is an opalized shell. The quality of the opal and completness / integrity of the fossil dictate the price. Pictures ???

 

[winyan]

Thanks again, AnA, and I'm checking to see if she does, indeed, have pics!

Thank you!

win

 

[Richard M.]

Australian opal deposits in the Great Artesian Basin frequently contain fossils of marine life that have been partially or completely replaced by common or precious opal. Some of the brightest and most valuable opals are often shell replacements. Clam shells (like the accompanying image) are best known but there are many others: snails, cephalopods, belemnites, even the famous opal "pineapples" that are believed to be opal replacements of what were once crystallized specimens of the mineral glauberite.

One of my favorite precious opal fossils is the rib "cast" of a Mesozoic plesiosaur, pictured in Fred Ward's book "Opals." The original bone material left a "mold" opening in surrounding rock after decomposing. The opening was later filled by silica-saturated water that resulted in precious opal of very high quality when the water evaporated. Precious opal frequently replaces wood or even "molds" left by mammalian and other fossils.

 

[winyan]

Thanks to you too, Richard M.!! I'm very appreciative of the additional info!

win

 

[Richard M.]

Hi Winyan,

I'm glad the information helped. The accompanying image is a precious opal pseudomorph of a belemnite. The Aussie opal miners often inaccurately call them "squid."

Richard M.