Limestone
A sedimentary rock composed mainly of calcium carbonate. It often forms from accumulated remains of shells and coral, and slowly dissolves in water to create limestone caves.
The Great Pyramid of Giza looked nothing like today: built around 2560 BC, it was sheathed in polished white limestone from Tura — mirror-smooth, reflecting desert sun for kilometres. Medieval Cairo builders stripped most casing stones away from the 14th century onward.
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