Greenstone is a type of metamorphic rock that primarily consists of minerals like chlorite, actinolite, and epidote. It is typically formed from the alteration of basalt or other volcanic rocks under specific temperature and pressure conditions. Greenstone is often found in ancient geological formations and is significant in understanding the Earth's early crust. This rock is commonly associated with greenstone belts, which are regions of the Earth's crust that contain a mix of volcanic and sedimentary rocks. These belts are important for mineral exploration, as they often host valuable resources such as gold and copper, making them of interest to geologists and mining companies.