When we talk about sustainability in architecture today, we often find ourselves turning toward trendy “eco-materials”: timber, rammed earth, hempcrete, recycled composites. These are all fine choices, of course — natural, renewable, and fashionable in their own way. But in our enthusiasm for the new, we seem to have forgotten the most sustainable building material of all: stone. Stone is so fundamental, so ancient, and so deeply woven into the history of building that its vi