Minerals EQ: How are minerals a part of rocks?

Of the almost 4000 known minerals, only about 30 are common. The most common are quartz, feldspar, mica, and calcite.

What is a Mineral?  DEF: A naturally occurring, inorganic solid that has a crystal structure & a definite chemical composition.  Example: Quartz

Naturally-occurring  Never man-made  Ex: Like rocks

Inorganic:  Means the mineral cannot come from things that were once living  Non Example: Coal – it is organic because it comes from plants that lived millions of years ago.

Solid  Definite shape, definite volume  A 3-D geometric figure  Not a liquid or a gas!

Crystal:  The repeating pattern of particles, line up when they form  Like a snowflake pattern or rock candy

6 Different Crystal Systems:  Cubic Ex: Magnetite  HexagonalEx: Quartz  TetragonalEx: Rutile  OrthorhombicEx: Sulfur  MonoclinicEx: Azurite  TriclinicEx: Microcline Feldspar

Definite Chemical Composition  Certain elements form together in specific ways  Like Hydrogen & Oxygen (H2O) and Carbon & Oxygen (CO2) form together to make these compounds

Physical Properties Identify Minerals  Physical Properties include several “tests” you can perform on minerals to determine what type of mineral they might be.

1. Streak Test  The color of the mineral’s powder that’s left behind when it is rubbed across a rough surface  Example: Pyrite looks like gold but, it’s streak looks greenish- black (aka “fool’s gold”)

2. Luster  Describes how light is reflected from the mineral’s surface. What does it look like?

Types of Luster  MetallicEx: Galena  GlassyEx: Topaz  Waxy, Greasy, PearlyEx: Talc  DullEx: Graphite  SilkyEx: Malachite  EarthyEx: Hematite

3. Density  It’s a calculation (math problem!)  Use a balance to find the mass  Place the mineral in H2O to find the amount of water it displaces. This amount is the volume of the mineral.  To find the density, divide mass by volume  Ex: Sample of Olivine  Mass = 237 g Volume = 72 cm3  Density = 237 g/ 72 cm3 = 3.3 g/cm3

4. Cleavage  One way minerals break  Easily split along flat surfaces  Ex: Mica & Feldspar

5. Fracture  One way minerals break  Break unevenly in irregular ways  Chipped  Shell-like Ex: Quartz  Jagged points Ex: Copper & Iron  Crumbles Ex: Clay

6. Mohs Hardness Scale  A scale that ranks 10 minerals from softest to hardest. You can compare unknown minerals to the minerals on this scale  Hardness can be tested by a Scratch Test  A mineral can scratch any other softer mineral  It can also BE scratched by any harder mineral  Softest Mineral – Talc  Hardest Mineral - Diamond

Color is the most easily observed mineral property and the least useful! Some exceptions to the color rule would be cinnabar, which is always red, and malachite, which is green.

Many minerals have a similar color.

For example, pure quartz is colorless or white, impurities can make the mineral rose, purple or pink!

Malleable Magnetic Radioactive Flourescence Taste

Minerals that can be hammered thin or shaped are said to show these properties. Can you think of a mineral that might be shaped or hammered? GOLD

Some minerals that contain Iron, are magnetic and can be picked up by a magnet.

This is the state of glowing while under a ultraviolet light. Some minerals even glow once the light is turned off!

Some minerals, such as this uraninite, are radioactive. They give off subatomic particles that will activate a Geiger counter.

Halite (rock salt) can be identified by its taste. This practice is not recommended!

Discuss the following! How many of the characteristics of minerals can you name? Why isn’t color a very good property to identify most minerals? Luster, color, streak, malleable, cleavage/fracture, taste, fluoresence, magnetic, hardness, and density Some minerals have similar colors

Discuss the following! There are four common minerals, how many can you name? Of the four common minerals, which one makes up over 60% of the Earth’s crust? quartz,feldspar,mica, and calcite feldspar

Discuss the following! Does this mineral show cleavage or fracture? Of the four most common minerals, which is the highest hardness? Cleveage quartz

How Earth’s surface forms  Minerals make rocks  EX: Granite may be made of many different minerals (feldspar, mica, hornblende, quartz)  Rocks are classified by how they are formed  EX: Igneous rocks form from magma/lava cooling  d. Different processes change rock & the surface of the Earth  EX: Weathering & Erosion break down rocks & move them to new places