Chapter 3Minerals

Updated November 2011

What is a Mineral?

• Mineral- a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition

Mineral – Naturally Occurring

• Must occur in the natural world

• Which of the following is naturally occurring?– Plastic– Brick– Glass– Quartz

Mineral - Inorganic

• The mineral cannot form from materials that were once part of a living thing. (Living things are said to be organic)

• Is coal a mineral?• How does coal form?

How Coal Formed

Mineral – Crystal Structure

• Crystal structure - the repeating pattern of a mineral’s particles forms a solid.

• A crystal has flat sides (faces) that meet at sharp edges and corners.

Question # 7on the study guideThis will not be on the test

• What does it mean when a mineral always contains certain elements in definite proportions??

• It means that the mineral has a definite chemical composition.

• What?? Next slide:

Are almost all minerals compounds??• Yes! This means that they are made up of more than one chemical.Some are pure though:

Question # 9: Name three pure crystalline elements:GoldSilverCopper

Mineral Identification

There are 8 properties used to identify minerals.

They are:1.Color2.Streak3.Luster4.Density5.Hardness6.Crystal Systems7.Cleavage and Fracture8.Special Properties

Mineral ID…

• Color – look at the mineral!!

Mineral ID…• Streak – the streak is the color of its powder.

To obtain this, rub the mineral against an unglazed porcelain tile. – (The color of the streak is sometimes different

than the mineral)

Mineral ID…

• Luster – describes how light is reflected from a mineral’s surface

There are 6 lusters of minerals

1. Metallic

2. Glassy (waxy, greasy, pearly)

3. Submetallic

4. Dull

5. Silky

6. Earthy

Mineral ID…• Hardness – use Moh’s Hardness Scale• Page 71 in the textbook• Find hardness through a scratch test

Moh’s hardness scale cont.…

Hardness can be determined by a scratch test. A mineral can scratch any mineral softer than itself. (But not any mineral harder)Example: To determine the hardness of azurite, you could try to scratch it with talc, gypsum, or calcite. But you discover none of them scratch it. Apatite, rated 5 on the scale does, therefore azurite’s hardness is about 4.

Mineral ID…Crystal Systems – 6 systems found on page 73 of the textbookThey are: 1.Cubic2.Hexagonal3.Ortrhorhombic4.Monoclinic5.Tetragonal6.Triclinic

Mineral ID…Cleavage and Fracture is the way a mineral breaks apart.•Cleavage = a mineral that splits easily along flat surfaces

• Fracture - how a mineral looks when it breaks apart in an irregular way

Mineral ID…

• Special PropertiesFluorescence- Glows in UV lightMagnetism- Attracts ferromagnetic materialsAcid Test- reacts chemicallyOptical Properties- bends lightRadioactivity- produces its own energyElectrical properties- conducts electricity

Section 2 page 76How minerals form

What is magma and lava?Magma- molten material from inside the earth that hardens to form rock.Lava- is magma that reaches the surface.

Minerals from magma and lava

How do minerals form from magma and lava?Minerals form as hot magma and lava cools inside the earth, or as lava hardens on the surface. When they cool, they form crystals (minerals).

Minerals from solutions

Solution- a mixture in which one substance is dissolved in another. Examples: salt water, iced tea mix, sugar water.

Minerals formed by evaporationHow are minerals formed by evaporation? When water evaporates from a solution it leaves behind the dissolved crystals (minerals). Example: when water evaporates out of a salt water solution- pure salt will be left behind.

How can minerals be formed from hot water solutions? Sometimes magma deep underground can get water very hot causing elements to dissolve. When the solution cools it causes the elements to leave the solution and crystalize.

Add Crystal Size!