Ancient Limestone, natural finish.
Limestone is what happens when calcium precipitates out of water, and it can happen geologically or biologically, which is why you often find fossils hidden in the pattern.
This is also why it’s so porous, giving it great insultation properties but also allowing stains to seep into your floors rather easily.
6000 years ago temples were built with Limestone in Malta. The Sphinx was built from Limestone and more recently, the Empire State building and St Pauls Cathedral were with Limestone.
You’re in good company if you have Limestone floors, and here’s how to look after them.