Galle Fort Dutch rampart stone types: coral rag vs laterite (Kabook) vs quarry granite durability?

The Dutch sea walls of Galle Fort (constructed between 1663 and the 1720s) incorporate three distinct geological materials tailored to defense. The seaward-facing revetments (Point Utrecht and Flag Rock) are armored with dense charnockite granite boulders brought from interior quarries to withstand direct Indian Ocean breaker impact. The internal core and sheltered landward ramparts employ dead coral rag quarried from the bay; its high porosity absorbs explosive cannonball energy without shattering. Parapets and interior soldier barracks use cut blocks of ferruginous laterite (Kabook), which harden upon exposure to air and bond seamlessly with slaked shell-lime mortar.