<p>Shale, a well-known problematic geomaterial, is influenced by the existence montmorillonite content owing to easy degradation or slaking when in contact with water. Slaking test using slake durability apparatus has been used to quantify the slaking behaviour of shale material. Some previous slaking studies have shown that the shales in Indonesia have extremely low to medium durability with a durability index of less than 50% for shales that formed during the Miocene Epoch. The shales were reported to have high montmorillonite content that contributes to the slaking process and low quartz content that contributes to the durability rate. On the contrary, shales of Pamaluan Formation has low montmorillonite content and higher quartz. This paper describes the slaking behaviour of shale material in Nusantara, Indonesia's New Capital City, as a major concern of the construction and sustainability development belonging to the Pamaluan Formation, formed during the Oligocene to early Miocene epoch, earlier than common shales. The research focuses on the influence of natural water content at the initial state (before the test) using the slaking test and the mineral composition of shale on its slaking behaviour. There are some important findings which make this shale different from other common shales originated from the Miocene Epoch. The durability index (I_d(2)) of shales in the Pamaluan Formation (Pamaluan Shale) is 70% in average, showing the shale material has medium to high durability or more durable rather than shales found in Java Island. The natural water content highly affects the slaking behaviour, where shales with an initial natural water content of more than 4% are easily degraded. The slaking potential and slaking rate are higher for higher natural water content. Furthermore, while the slaking behaviour of common shale is dominated by montmorillonite content, several mineral tests of these on the contrary indicate presence of more than 55% quartz and less than 1% of montmorillonite content. Although the montmorillonite contents are very low, the existence of montmorillonite and other clay minerals in the middle among quartz affect the disintegration process and slaking behaviour of the shale. The high content of the quartz increases the shale's durability. It is concluded that the slaking behaviour of Pamaluan Shale material is affected by its natural water content at the initial stage and mineral composition.</p>