Interesting object... whatever mollusk it may come from.
I am not sure if
Ambra Greco are represented in the States at all. If so, they carry a collection of conch pearl jewelry. Although overall prices are high as expected from signed jewelry, their offer makes good reference because of volume and variety. One of the sellers posting here has some too - all of traditional traits.
That pearl would be huge, but there is no color and no pattern... If the seller of that one chose to trade size for color so radically, it makes an unusual choice to me.
My 2c.