Minerals

Minerals

A mineral is any naturally-occurring, inorganic solid that has a definite chemical composition and an orderly crystalline structure.

What is a Mineral?

In order to be classified as a mineral a substance must meet 5 specific criteria.

We will follow the mnemonic device "D.I.N.O.S." to help you remember them.

D = Definite Chemical Composition

• A mineral must have a specific chemical make-up.

Multiple Choice

Which of the following is an example of a mineral having a definite chemical composition?

• Quartz may display a variety of colors but always has the basic building block silicon dioxide (SiO₂).

• Pyrite forms cube-shaped crystals.

• Concrete always has limestone crushed into its mixture.

I = Inorganic

• A mineral may not came from anything living or once-living.

Multiple Choice

Which of the following is inorganic?

• Calcite

• Petrified wood

• Coal

• Fossil-bearing shale

N = Naturally Occurring

• A mineral must be formed by a natural process, it cannot be man-made.

Multiple Choice

Which of the following is a naturally occurring mineral?

• Concrete

• Glass

• Ice from your freezer

• Ice in a glacier

O = Orderly Crystal Structure

• A mineral's atoms must be arranged in an orderly pattern.

The arrangement of sodium and chlorine atoms in the crystal structure of halite...

...is evident is the shape of its crystals.

Multiple Select

Check each of the following that is an example of a mineral's orderly crystal structure?

• Iron and sulfur form an ionic bond and crystallize into cube-shaped crystals called pyrite.

• Sodium and Chorine form an ionic bond and crystallize into cube-shaped crystals called halite (salt).

• Copper is often found as irregularly-shaped "nuggets".

• The mineral sulfur smells like rotten eggs.

S = Solid

• A mineral must be a solid substance, it may not be a liquid or gas.

Multiple Select

Under which of the following conditions would water (H₂O) be classified as a mineral? (Check all that apply)

• Snowflakes falling from the sky.

• A stream flowing over rocks.

• Ice cubes in your freezer.

• Ice in a glacier

• Ice in a comet

If a substance does not meet all the cirteria of "D.I.N.O.S."...

...it is NOT a mineral.

Multiple Choice

Which of the following is NOT one of the "D.I.N.O.S." criteria?

• Definite origin

• Inorganic

• Naturally occurring

• Solid

What properties define individual minerals?

Mineral Properties

• Minerals can be identified through a series of tests of their various properties.

The tests we will use in this class are...

• Hardness

• Cleavage/Fracture

• Luster/Color

• Streak

• Density

• Crystal Form

• *Other Tests

Test for Hardness

• A mineral's hardness is a measure of its resistance to being scratched by another mineral or other object.

• The Mohs Hardness Scale is used as a baseline for mineral hardness.

Multiple Choice

Which of the following minerals tops the Mohs Hardness Scale at a 10?

• Diamond

• Calcite

• Corundum

• Talc

Multiple Choice

Which of the following minerals would be scratched by all of the others on the Mohs Hardness Scale?

• Talc

• Diamond

• Gypsum

• Apatite

Test for Cleavage/Fracture

• Cleavage is a mineral's tendency to break along flat, even surfaces due to a plane of weak chemical bonds.

• Fracture is a mineral's tendency to break into uneven, irregular surfaces.

Multiple Select

Check all of the minerals pictured that display cleavage.

Multiple Select

Check all of the minerals pictured that display fracture.

Test for Luster/Color

• Luster is a test of how light is reflected from the reflected from the surface of the mineral.

• Color is a noticeable quality that can indicate the presence of different elements within the mineral.

Multiple Choice

What type of luster does this mineral display?

• Earthy

• Pearly

• Vitreous (glassy)

• Metallic

Multiple Choice

Which type of luster does this mineral display?

• Metallic

• Earthy

• Waxy

• Silky

Test for Streak

• A mineral's streak is its color in powdered form.

Test for Density

• A mineral's density is determined by dividing its mass by its volume.

Multiple Choice

A mineral sample has a mass of 35g and a volume of 10cm³. Which of the following is the correct way to calculate it's density?

• 35g/10cm³ = 3.5 g/cm³

• 35g X 10cm³ = 3.5 g/cm³

• 10cm³/35g = 3.5 g/cm³

• 10cm³ X 350g = 3.5 g/cm³

Multiple Choice

Since our sample in the last problem was determined to have a density of 3.5 g/cm3, if the sample is pure, then it is most likely to be which mineral?

• Fluorite

• Topaz

• Chalcopyrite

• Quartz

Test for Crystal Form

• When visible, a mineral's crystal form is an expression of a mineral's internal arrangement of atoms.

*Other Tests

• Effervescence

• Fluorescence

• Magnetism

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How are minerals formed?

The 4 common ways in which minerals form are...

• Crystallization

• Precipitation

• Metamorphic processes

• Hydrothermal processes

Crystallization

• As magma cools different substances solidify from the magma more quickly than others, creating a mix of different minerals.

• The longer a magma takes to cool the more different minerals are produced, and larger mineral crystals are able to grow.

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Multiple Select

Check all of the following that would result from a slow cooling magma.

• An igneous rock with many large mineral crystals

• An igneous rock with mostly small mineral crystals

• An igneous rock with a variety of different minerals

• An igneous rock with a uniform composition

Precipitation

• (not to be confused with precipitation of water from clouds)

• Dissolved elements or ions carried by water will be left behind and crystallize together as water evaporates.

Multiple Choice

Which of the following is an example of a mineral forming by precipitation?

• Dissolved calcium, sulfate, and water molecules bond together as a lake evaporates, leaving behind deposits of gypsum.

• Superheated water cools and leaves copper deposits behind as it flows through cracks and fissures in rock.

• Tectonic activity buries a bed of rock deeper beneath the earth, increasing temperature and pressure on the rock, and causing micas in the rock to recrystallize.

• A body of magma cools slowly over time, allowing large feldspar crystals to form as it crystallizes into rock.

Metamorphic Processes

• Metamorphic processes involve changing the temperature and/or pressure of existing rock.

• Increasing temperature and/or pressure on a mineral causes its atoms to become unstable and rearrange into a structure more suited to the new conditions they are in.

Multiple Choice

Which of the following is an example of a mineral forming by metamorphic processes?

• Dissolved calcium, sulfate, and water molecules bond together as a lake evaporates, leaving behind deposits of gypsum.

• Superheated water cools and leaves copper deposits behind as it flows through cracks and fissures in rock.

• Tectonic activity buries a bed of rock deeper beneath the earth, increasing temperature and pressure on the rock, and causing micas in the rock to recrystallize.

• A body of magma cools slowly over time, allowing large feldspar crystals to form as it crystallizes into rock.

Hydrothermal Processes

• Hydrothermal activity causes super-heated water to move through cracks and pores deep underground.

• As it dissolves minerals and carries them through the rock until they cool and recrystallize. 

Multiple Choice

Which of the following is an example of a mineral forming by hydrothermal processes?

• Dissolved calcium, sulfate, and water molecules bond together as a lake evaporates, leaving behind deposits of gypsum.

• Superheated water cools and leaves copper deposits behind as it flows through cracks and fissures in rock.

• Tectonic activity buries a bed of rock deeper beneath the earth, increasing temperature and pressure on the rock, and causing micas in the rock to recrystallize.

• A body of magma cools slowly over time, allowing large feldspar crystals to form as it crystallizes into rock.

Open Ended

What question(s) do you have after participating in this lesson? Is there anything else you would like to know about minerals?

THE END

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