This is a terrific slab of Green Moss Agate. The slab has a milky translucent background with a heavy network of green and white lines throughout. There are a few areas with pits or voids in the darker parts of the slab but the lighter parts are complete.

It is about 6 mm thick.

Photographed wet to show details and dry to show the slab dimensions (second photo).  The dry photo is on a 10mm or 1cm to the square scale.