Kōrero: Rock, limestone and clay

This kiln at Sandymount on the Otago Peninsula was built in 1865 by a Scotsman named McDonald. During the 19th century lime was burnt in small kilns such as this, near the limestone deposits. Limestone, which is mainly calcium carbonate (CaCO₃), was burnt to drive off carbon dioxide (CO₂), leaving calcium oxide (CaO) – otherwise known as burnt lime. Crushed limestone was used to improve pastures, and burnt lime was used to make mortar.