* Sandstone Formation: Sandstone forms from sand grains that are cemented together. These sand grains often come from the erosion of older rocks, like granite.

* Intrusive Nature of Granite: Granite is an igneous rock that forms when molten rock (magma) cools and solidifies. Granite often intrudes into existing rock layers, pushing them aside.

* The Principle of Superposition: In geology, the Principle of Superposition states that in undisturbed rock layers, the oldest layers are found at the bottom and the youngest layers are found at the top.

Therefore, if sandstone is in contact with granite, the granite must have been there first for the sandstone to form on top of it.