...And light-coloured paving (like that in your photo) gets less hot than dark.
On that subject: denser material, such as compressed concrete slabs or basalt, may be harder wearing (not a hard a fast rule) but it also holds more heat; and given any particular thermal conductivity, that means it can feel hotter on your feet in summer (your feet will be less effective at cooling the stone). In fact, denser materials tend to have higher thermal conductivity, which makes matters worse. ...All from a summer perspective.
So the light coloured and relatively lightweight limestone is a cool choice, at it were.
One point to note with limestone: For paving, it is obviously preferable to have a rock which splits to give decent parallel sided stones. But if you pick one which is too well laminated, chances are it will be prone to splitting along the laminae of its own accord after you have laid it (especially after winter rains then summer scorching). That means your slabs will gradually erode, leaving shallow 'walls' of concrete pointing. Better to find limestone that has distinct thin beds (say 4-6cm thick) separated by localized laminae. That way, you'll get decent flat faces and solid paving stones.
No - don't ask me where to find such rock! Half the fun is in exploring (because you never know what you might find that you weren't looking for).
And water-worn, as in your photo, is useful because it is:
- gentler on the feet
- easier to sweep (perhaps)
- already tested for being over-laminated (if it had weak laminae, the water-wearing process would probably have split the rock already)