Dike in a granite main content.

Dike in a granite

Dike in a granite

Exhibition Text

This rock is a granite that solidified between 350 and 320 million years ago. More than 120 million years later, molten basaltic rock forced its way upward through a fracture to form a gray-black dike in the granite. Note the difference between the fine-grained margins of the dike, which cooled quickly against the cold granite, and its coarser-grained interior, in which slower cooling allowed crystals to grow larger.

Provided by Royalty Granite, Elberton, Georgia

For Educators

Topic: Earth Science

Subtopic: Earth Formation/Evolution

Keywords: Dikes (Geology), Magmas, Granite

Audience: General