These are the three categories of rocks and minerals: Igneous, Sedimentary, and Metamorphic. This is what I’ve learned about them.
Igneous rocks are rocks that were melted and then it hardened. The word igneous comes from the latin word ignis meaning “fire”. A lot of the earth’s crust is made up of feldspar, mica, and hornblende mixed in.
Sedimentary rocks makes up most of our cliffs. Sedimentary rocks contain most of the worlds fossils and petrified wood. Shale is made up of cemented particles of clay and a little bit of silt. Sandstone has particles that are just big enough to see and are made mostly of quartz sand. Conglomerate has bigger pebbles-bolders that are cemented together.
There are 2 types of chemical sedimentary rocks, Organic and Inorganic. Organic comes from things that were once living, and inorganic are made up of things that were never living. Organic limestone has some inorganic limestone, but most of it is organic. Chalk is made from the shells of single celled organisms that have been deposited. Coal is the altered remains of huge masses of buried plant material.
Inorganic limeston is made the same way as stalactites and stalagmites. They form were the water has a great deal of mineral material dissolved in it such as in caves or around mineral springs. Dolomite is a rock similar to limestone, with atoms of magnesium. When sea water evaporates, it leaves behind solid minerals like salt.
The greek word meta means “change”, and morphe means “form”. These 2 words put together means “to change form”, some rocks will metamorphose into something different. When shale gets heated it turns into slate, which is used for blackboards. Some people think that schist is metamorphosed slate but they are not quit sure yet. Gneiss (pronounced nice) is a highly metamorphosed rock with bands of different colors. Limestone changes into marble and marble is very pretty especially when it is polished.