The reserves of Gabbro and Siltstone are geographically distributed all over the world. Gabbro and Siltstone reserves play an important role in a country’s economic growth. Rocks are deposited according to the topography of the area. Some oldest rocks can be found in the Canadian Shield, Australia, Africa and in a few other old regions around the world. The ages of these felsic rocks are around 2.5 and 3.8 billion years. Learn about the countries with Gabbro and Siltstone reserves here.