Before we look at rocks, let’s review the characteristics of minerals. Naturally occurring Definite crystalline structure Definite chemical composition Solid Inorganic Used for building materials, gemstones, health supplements, toothpaste, medical, baby powder, etc.
What do you know about rocks? Do you agree with these statements? Rocks are hard. Rocks are solid. Rocks are natural. Rocks are made of minerals.
Rocks are hard. Not always… Some rocks are soft and can be scratched with your fingernail (shale, gypsum) Other rocks are soft until they are exposed to air, or visa versa.
Rocks are solid. Not always… Some rocks contain water in pores. Geodes hold water and minerals inside. Some igneous rocks are threaded or have fine meshwork, like Pele’s hair.
Rocks are natural. Not always… Consider everything that humans make.
Rocks are made of minerals. Not always… Remember that minerals are made of inorganic material. What about coal? What about coquina? What about obsidian?
So what are rocks then???
How are rocks classified? How they are formed! Igneous – melting, cooling, and hardening Metamorphic – heat and pressure Sedimentary – WEDCC
We will look at these in depth over the next few weeks.