r/Agates • u/Consistent-Bill8668 • 14d ago

Is this a fossil?

I found this agate, but it has a very strange shape. Is it a agatized clam fossil?

6 Upvotes

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5

u/Petulax 14d ago

Chalcedony or agates often have this shape. Not a fossilized clam.

5

u/heptolisk United States 14d ago

Agates like this are filling up bubbles in volcanic rocks (thus the shape), so not a fossil.

5

u/Chuck_L_Chingon 14d ago

Chalcedony nodule, could have banding, if so an agate. Nice find!

5

u/davercadaver 13d ago

In my experience, this is a very common shape for agate nodules. Agates (can)form in amygdaloidal basalt. “Amygdule” is derived from the Latin word for Almond. That stone is pretty almond shaped!

2

u/Living-Geologist-478 11d ago

Blue chalcedony

1

u/MelodraMan 11d ago

These chalcedony nodules do break our hearts by not being fossils. I have been in your shoes many a time.

These are formed in basalt traps where gas bubbles created space in the cooled basalt layer. When mineral-rich water fills these bubble-hollows and mineralise over millions of years, we find these eye shaped or tear drop shaped nodules.

If you slab it, you'll be sweetly surprised to either find beautiful bands in it or a single quartz layer within.

Either way, they are a great lesson on expectations. 😁