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THE EARTH'S CRUST
The whole earth is made of rocks and minerals. Inside the earth there is a liquid core of molten rock and on the outside there is a hard crust. If you compare the earth to an apple, the skin on the apple is like the crust on the earth. It is not very thick, but to us it’s big. You would have to dig upwards of 35 km (21 miles) to reach the next layer of Earth.
The Crust makes up less than 1% of the total mass of the Earth. It is made minerals, but we know them as elements. The 8 elements that make up the Earth’s crust are… 4 6.6% Oxygen (O) 2 7.7% Silicon (Si) 8.1% Aluminum (Al) 5.0% Iron (Fe) 3.6% Calcium (Ca) 2.8% Sodium (Na) 2.6% Potassium (K) 2.1% Magnesium (Mg)
The Mantle is the solid casing of the Earth and it makes up about 69% of the Earth’s mass. It is also made up of minerals like silicon, oxygen, aluminum and iron.
The Core is mainly made of two main minerals iron and nickel. The core only makes up about 30% of the Earth’s mass.
- If you were to dig in the ground what part of the Earth would you be digging in?
MINERALS
Minerals must occur naturally. This means man‐made substances such as steel aren't minerals. Minerals are Inorganic substances, which means that are not living and are not formed by living processes such as eating or growing.
A mineral is composed of the same substance throughout. If you were to cut a mineral sample, it would look the same throughout. You may have seen rocks that have different colors and insides, but minerals are different. They have the same elements, colors, and shapes throughout the entire sample. Think of a diamond. It has the same element (Carbon) in the same structure, all the way through it. Rocks are actually made up of two or more minerals that’s why they have different colors, shapes and textures.
There are about 4000 different minerals in the world. Minerals are made of elements ‐ either a single element or a combination of the 92 naturally occurring elements. Remember we learned about the periodic table of elements….that helped us prepare for this topic ☺.
Minerals are sorted into 8 groups. The following list includes the group name with some common minerals from that group. Don’t get hung up on the names, just look at the different types and the common ones that go with it.
- Native Elements ~ copper, silver, gold, nickel‐iron, graphite, diamond
- Sulfides ~ sphalerite, chalcopyrite, galena, pyrite
- Halides ~ halite (salt NaCl), fluorite
- Oxides & Hydroxides ~ corundum, hematite
- Nitrates, Carbonates, Borates ~ calcite, dolomite, malachite
- Sulfates, Chromates, Molybdates, Tungstates ~ celestite, barite, gypsum
- Phosphates, Arsenates, Vanadates ~ apatite, turquoise
- Silicates ~ quartz, almandine garnet, topaz, jadeite, talc, biotite mica
The most abundant mineral on Earth is quartz. It makes up all the sand found on beaches and deserts.
We can tell the difference between the different minerals by testing their physical properties. Each group of minerals will have different properties. As scientists we will look at those properties to help us identify the minerals.
- What are some things you think we can test at to help us tell minerals apart? (Think, how would you tell different rocks apart?)
- What are some minerals you recognize from the list found above?
Crystals
Crystals are minerals that have had the chance to grow in the shape that they were meant to be. Just like your DNA determines the color of your eyes, how tall you will get to be and the shape of your bones, the elements that a mineral is made of determines what shape it gets to be. We can tell different minerals apart by what crystal shape they are.
Most of the earth's crystals were formed millions of years ago. Crystals form when the liquid rock from inside the earth cool and harden. Sometimes crystals form when liquids underground find their way into cracks and slowly deposit minerals. Most mineral crystals take thousands of years to "grow" but some like salt (halite or halides) can form so quickly that you can watch them grow at home!
Think about the properties of quartz:
- Hard
- Rigid
- Impermeable
- Transparent (see‐through)
Pots and pans Pots and pans are made from metal - stainless steel, cast iron, copper or aluminum. All of these come from minerals. But did you know that the non-stick coating you find on many pans is also made from a mineral?
Fluorine is used to make non-stick Teflon ® and comes from the mineral fluorite. The same coating can even be found on your winter coat to keep it clean and waterproof.
Think about the properties of pots and pans:
- Strong
- Impermeable
- Do not rust
- Conduct heat
Just to review a mineral is...
- Inorganic , this means that it is not made by a living organism.
- A solid. There is one unusual exception. Native mercury is a mineral and is the only metal that is a liquid at normal temperatures.
- Has a crystal shapes that can be identified.
- Made by nature which means minerals are not made, directly or indirectly, from human activity.
- Have the same chemicals in the same order all the way throughout the sample.
- Ask your parents or family: What is around the house that is made from minerals?
- Circle the minerals
Diamonds Steel Iron Fluorine Bleach Mercury
Salt Sand Amber Wood Gold Topaz
Rubber Glass Leather Graphite Plastic Stalactite
