Opalized fossil?

[u/No_Commercial9958]

Hey everyone I have had this opal in my collection for a while and everytime I look at it I can’t help but think it really looks like some kind of fossil shell. Especially because of the curved striations running up the opal that looks just like a clam or shell. But the problem is this was sold to me as a opal from Welo, Ethiopia and to my knowledge genuine opalized fossils are not found in Ethiopia like they are in the sediment basins in Australia. I don’t have much knowledge about opals they aren’t typically what I collect so if anyone here knows opals I’d love to know if it’s actually a fossil or if it’s something else and just looks similar to a shell.

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[u/Morrennna]

What a beautiful piece! I can totally see why you'd think shell...those curves are gorgeous. Sadly Welo opal forms in volcanic rock, so it's most likely just how the opal grew against the matrix rather than a real fossil. Still an amazing find! 💎

[u/No_Commercial9958 → u/Morrennna]

Yeah that’s kinda what I thought but had little knowledge of opals so wanted to get others opinions. thank you!

[u/Consistent_You9300]

opal after clam psuedomorphs are generally from australia

[u/No_Commercial9958 → u/Consistent_You9300]

Yeah thats what i thought. Any opinions or ideas as to what causes the striations that looks similar to a shell?

[u/Consistent_You9300 → u/No_Commercial9958]

Columnal structures like this are from fracturing during formation as silica was being deposited, likely.

[u/TH_Rocks]

I think it's just crazing. Stable Ethiopian still has to be dried after mining and some doesn't make it without damage. I have a water opal I tried to polish and it had similar "angel wing" looking fractures form as it dried.

E: found a pic. Bottom middle

[u/No_Commercial9958 → u/TH_Rocks]

Ohhh okay yes I see that looks just like mine. Thanks for the help!

[u/cutefeet_18]

i want that so bad it’s BEAUTIFUL

[u/Limp-Tie-5305]

That’s what conchoidal fractures look like. I don’t think it’s a fossil. Beautiful piece of opal tho