Stromatolites are large formations of rocks that have been formed by the growth of multiple layers of bacteria over a very long period of time. These usually take the shape of mounds, columns and sheets. Cyanobacteria, s... More »

The rock cycle explains the changes rocks undergo from the time they are expelled from the earth's mantle in the form of magma to the time that they return to the mantle and become magma once more. This process takes pla... More »

Sedimentary rocks are made of minerals and debris that have been weathered or eroded from rocks over long stretches of time. This sediment can be laid down by water, by the movement of earth or glaciers, by evaporation o... More » Science Earth Science Geology

Geologists study the Earth and its physical formations and materials. This includes the layers of the earth, surface features like mountains and volcanoes and historical materials like rocks and fossils. More »

Citrine geodes are naturally occurring crystal formations that have a pronounced yellow or orange tint. The crystals inside the geode cavity are usually a form of amethyst that has been subjected to high temperatures by,... More » Science Earth Science Geology

Talc is a common mineral which is widely known for its use in talcum powders, for its softness, and for creating pseudomorphs of other minerals in rock formations. It is not considered a gemstone and is often used for in... More » Science Earth Science Geology

Igneous rocks that are allowed to cool more slowly form larger crystals, while igneous rocks that cool quickly form smaller crystals. It is simply a matter of time. The longer it takes for magma to cool, the more time is... More »