There is little ambiguity about what this is - freshwater (nucleated? two of them fused?). But it sure is large: 30mm x 11mm! Now, the shape makes it more of a curio and the price hints at better cousins hiding somewhere. Sure wish it has better cousins somewhere!
Here's the thing:
LINK
This forum has worked wonders for me so far, but there's still work for me to get comfortably confident about pearls. I hope you don't mind these posts of what seem unusual 'finds' to me.