Minerals

We learned that sedimentary rocks are made of sediment. What is sediment made of? The answer is minerals. Sand for instance is made up of mostly quartz grains. Quartz is a mineral. Igneous rocks and metamorphic rocks are also made out of minerals. There are thousands of different minerals. They can be elements or compounds. In order to be considered a mineral, the substance must be…

Solid

Naturally Occurring –cannot be man made. Plastic is not a mineral.

Organized atoms- atoms are organized in a way that gives the mineral characteristic shapes.

Inorganic - Cannot be made from any living thing.

Definite chemical makeup- Made of only one type of substance. Ex. Quartz is only Silicon and Oxygen—SiO₂. Gold is only made of Gold atoms..Au. Galena is only lead and sulfer…PbS.

How to identify a mineral!

• There are lots of ways to help determine the identity of a mineral.

1. Hardness- how hard the mineral is compared to others.

• Things that are harder than the mineral will scratch that mineral, and things that are softer than that mineral will not scratch the mineral. Scientist use things like pennies, glass and their fingernails to help determine the hardness of a mineral. Moh’s scale is used to determine the hardness of a mineral.

2. Color- the color of the mineral.

• The color of a mineral can often be used to identify a mineral. Gold is gold in color, quartz is clear. This method is not always effective though because other minerals can also be gold colored for example, and quartz is sometimes purple, pink are grey.

3. Streak-color of the powder when rubbed on porcelain.

• The steak of a mineral is always the same. When you rub some minerals across a porcelain plate, a streak is left behind. Graphite leaves behind a gray streak. The color of the steak is not always the color of the mineral.

4. Luster- how a mineral’s surface reflects light.

• Luster can be metallic or nonmetallic. Minerals that have a metallic luster look like a piece of metal. Some minerals do not look like metal. They can look glassy, waxy, dull, or brilliant.

5. Density- the mass per unit volume.

• Density is how compact the molecules that make up the mineral are. You find it by dividing the mass by the volume. The answer is in g/ml. Minerals have a specific density no matter what the size…for example gold is always 19.3 g/ml.

6. Fracture-how a mineral breaks when dropped

7. Cleavage- tendency to split along smooth surfaces.

8. Magnetism- some minerals can be magnetic and attract iron.

9. Acid test-some minerals fizz when acid is poured on them.

10. Shape-some minerals have certain shapes, like a cube, or a hexagon.