https://www.sciencenews.org/article/sca ... ystals-see
The article continues with other fascinating details about the mirrors.Magazine issue: Vol. 193, No. 1, January 20, 2018, p. 8
There’s stiff competition for the most elaborate eyeballs in the animal kingdom, but a mollusk that turns up on dinner plates might be a finalist.
Each of a scallop’s eyes — it has up to 200 of them, each about a millimeter in diameter — contains millions of perfectly square, flat crystals that build up into a mirrored mosaic, new research shows. And that shiny surface is curved in a way that lets a scallop focus light onto two different retinas.
It's a short article, well worth the read.