There are lots of types of rock and each type has different properties and uses. For example, some are strong and hard but others are soft and sandy. Some rocks are harder than others. For example ...

Large crystals found in geodes and other rocks are relatively ... Chalcedonies include many types of cryptocrystalline quartz gems and feature a number of different colors. Geologists can tell ...

Curious Kids is a series for ... There are three main rock types: igneous, sedimentary and metamorphic. These rocks are made ...