Tessellation. And cubes or 6-pointed stars or both, at least. I love the moons. They seem unusual. Islamic rather than Christian? But then again, the moon is a pretty universally used and understood symbol. And then again (again) — it’s not quite moon-like. The moon never looks like that, like it has a bite taken out of it, a perfectly circular bite. Oh, I do love a mystery. This is a floor in the library mentioned earlier.
Regarding the floor in the *main*cathedral, here’s what Leila Firusbakht says at this link: http://www.turismo.intoscana.it/allthingstuscany/tuscanyarts/siena-duomo-mosaic-floor/
“Crafted by about forty artists and artisans between the 14th and 16th centuries, the 56 panels that constitute the floor vary in size and shape – most of them have a rectangular shape, some a hexagon or a rhombus one – and are made mainly by two different techniques: one known as graffito (tiny holes and cutting lines created in the marble and then filled with black stucco and mineral pitch) and the one called“marble intarsia” (black, white, green, red and blue marble employed in much the same manner as wood inlaying).”
You can see lots more photos of floors there. Enjoy…