MINERALS

UNIT VIII: MINERALS

After UNIT VIII you should be able to:

o Understand how mineral crystals acquire their shape

o Understand the characteristics that define a sample as a mineral

o Understand that many minerals are composed of similar elements

o Understand the connections between minerals and rocks and that many rocks contain similar minerals

o Utilize the ESRT to determine human uses of common minerals

o Understand and be able to perform common mineral identification tests such as:o Coloro Streako Breakage (cleavage or fracture)o Hardness (Mohs Scale)o Acid testo Magnetism testo Lustero Density

o Elemento Atomo Chemical

Compositiono Mineralo Rocko Organico Inorganico Orderly

arrangemento Solidificationo Lavao Magmao Igneouso Precipitateo Evaporateo Sedimentaryo Metamorphico Crystallizeo Crystalo Appearance

o Hardnesso Mohs Scaleo Lustero Metallico Non-metallico Streako Powderedo Crushedo Breakageo Cleavageo Fractureo Densityo Masso Volumeo Acido Reactiono Magnetico Abrasiveo Lubricant

UNIT VIII vocabulary you should be able to use and understand:

o Scratcho Impuritieso Oxidationo Angularo Physical

propertieso Chemical

properties

5 Fundamental Mineral Characteristics

Definite chemical composition Orderly arrangement of atoms Naturally occurring Inorganic Solid

What is a mineral?

Minerals have a definite chemical composition unique to that mineral

The chemical properties a mineral possesses determines what humans use that mineral for

For example, the mineral gibbsite (Al(OH)3) can be processed to release the aluminum atoms within it to be used in manufacturing

Mineral Composition and Uses

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Definite Chemical Composition

The same elements will make up the same minerals but impurities/oxidation may at times change their color

For example, table salt, or halite, is always NaCl…composed of a combination of sodium (Na) and chlorine (Cl) atoms

Other Mineral Uses

Jewelry Electronics Abrasives Lubricants A source of metal

(ore)/other useful elements

What are minerals made up of?

Minerals are composed of 1 or more elements

Certain elements contribute color to minerals (such as these quartz samples), but color alone is not a definite way of identifying them

Many minerals contain the same elements

Use your ESRT to identify the elements

Common Mineral Uses

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Orderly Arrangement of Atoms

Atoms are arranged in an orderly fashion so that a crystal forms

This arrangement defines a mineral’s physical properties such as crystal shape, hardness, or cleavage

For example: halite crystals and the atoms that produce them

Atomic Arrangement and Breakage

The bonds between atoms (internal atomic arrangement) in a given mineral determine how the mineral breaks

Even, angular breakage is known as cleavage

Uneven, rough breakage is known as fracture

The cleavage of the mineral graphite allows it to slide off in sheets when pressure is applied, thus making it ideal as a material in pencil lead.

Naturally Occurring/Inorganic Solid

Was not produced by life processes or humans

Is not a liquid or a gas

How do minerals form?

Minerals crystals form due to one of several rock-forming processes found in the rock cycle Cooling and

solidification of magma/lava

Precipitating out of a solution, such as when water evaporates leaving salt (halite) behind

Undergoing heat and/or pressure to form new minerals

Rocks are made up of 1 or more minerals

This granite has several minerals within it

Identifying minerals can be difficult, however many minerals can be identified with a combination of simple tests.

Mineral Identification: Appearance (color)

Color and appearance can help identify some minerals, but it is usually not enough

Gold

Pyrite

Common Colors

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Mineral Identification: Hardness

Hardness is a measure of how easily a mineral can be scratched

In our class “hard” minerals are able to scratch glass while “soft” minerals do not

Talc is a very soft mineral and can be scratched by a fingernail

Diamonds are the hardest naturally occurring material and can only be scratched by another diamond

Mineral Identification: Mohs Scale

The Mohs Scale assigns a number to a mineral’s hardness

A diamond is a ’10’ since it is the hardest mineral

Talc, being one of the softest, is assigned a ‘1’

Lower numbers more easily scratched

Hardness Values of Common Minerals

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Mineral Identification: Luster

There are two types of luster we are concerned with in this course: metallic and non-metallic

Metallic luster is when a mineral appears to be made of metal

Non-metallic luster can be a variety of other colors including minerals that look like glass

Luster of Common Minerals

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Mineral Identification: Streak

The streak of a mineral is the powder left behind when a mineral is crushed or is rubbed against an unglazed porcelain tile

Streak

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Mineral Identification: Cleavage and Fracture

Cleavage and fracture describe how a mineral breaks

Cleavage is a mineral breaking along a flat plane

Fracture is uneven and random breaking

Breakage of Common Minerals

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Mineral Identification: Density

Determining a mineral’s density sometimes help determine what it is

Recall: Density = mass/volume

Mineral Identification: Reaction with Acid/Magnetic

Some minerals bubble when acid is dripped onto them

Other minerals are magnetic

Other Distinguishing Characteristics

Use your ESRT page 16