How long does it take to petrify a clam?

Factual Questions
1

I have a petrified clam; I found it in my aunt’s yard on Orcus Island, WA. What I wonder is, how many millions of years did it take to get that way, and being a fossil, is it worth anything (money wise). If it was worth anything where would I shop it around? It’s a cool paper weight, though I think it might belong in a musiem.
Any thoughts?

2

Some suggest that mineralization of soft tissue can occur within weeks of being buried. Bone can start to undergo mineralization within months.

Oh, and in general, clams are one of the most common fossils, so as worth goes, most likely nothing.

3

Do you mean how old is the fossil, or how long does the fossilization process take? If the former, it could be anywhere from less than a million to over 500 million years old. If the latter, it depends on the type of fossil, it could have formed over several years to millions of years.

There are a bunch of websites online where you can buy fossilized shells for anywhere from a few dollars to a hundred dollars or more - if it’s some rare specimen it might be worth something to a collector, but the odds are it’s not really worth anything. Since they’re very durable to begin with and are quickly covered in sediment when the organism dies (many actually living their lives within the sediment), they’re very common fossils. I’m not a collector but I have a few I found in the woods when I was a kid.

I’m sure if you look online you’ll be able to find some sort of identification key to help you ID it. With that info it should be easy to see if what you have is valuable or not. If nothing else, at least you’ll know something about it.

4

Damn, I was sure this thread was about a euphemism.

5

On a coral reef, a few decades of coral and shell overgrowth will make it part of the fast reef. Couple of things:

  1. Best to use the term “fossilize.” Petrification is a specific term which entails a full replacement of the original substance by the precipitating mineral, whether silica or calcite. There is permineralization which simply means filling the empty spaces with either silica or calcite.

  2. Soft tissues are not likely to fossilize in any way. The only means are an efficient seal like amber (and amber can also disintegrate) or mummyfication. The best you have is for the mass to be burried, the soft part will dissolve away leaving a cavity, and that cavity will be filled by a more lasting susbtance. That way, you preserve the original form.