A dodo egg is a renewable food item that is randomly left behind by a dodo bird. Dodo eggs are large and oval in appearance with a light blue shell with a wavy pattern or darker areas.
As a result, rocks form quickly and mineral crystals are very small. Rhyolite is one type of rock that is formed when lava cools. It contains similar minerals to granite. However, as you can see in Figure 3.21, the mineral crystals are much smaller than the crystals in the granite shown in Figure 3.20.
Secondary minerals can also be formed during a purely physical change in the crystalline structure of a substance, retaining its chemical composition: cubic chalcosine changes to rhombic chalcosine, high-temperature cubic leucite changes to low-temperature rhombic leucite. There are various forms of secondary minerals. These are powdery or other masses or pseudomorphs which retain the external form of the primary mineral while the substance is replaced by a new one. Lazarenko, E. K. Osnovy geneticheskoi mineralogii.