Chapter 10 Minerals, Rocks and Soils

Unit 4 Earth’s Crust

Explain how society’s needs led to developments in technologies designed to use rocks.

Classify and describe rocks based on their method of formation: sedimentary, igneous, metamorphic

Explain various ways in which rocks can be weathered: mechanical, chemical

Classify minerals based on their physical characteristics.

Learning Outcomes

Minerals: naturally occurring inorganic solid materials,

composed of one or more elements

Rock: is a mixture of one or more minerals.

Minerals

Most minerals are quite rare.Only a few are common (ex: quartz & mica)

Minerals

MicaQuartz

A mineral can be an element (a pure substance) or a compound (two or more substances).

Some minerals are found in the earths crust (the outermost layer – this is where we live).

Granite is a type of rock that is made up of 4 different minerals. It is made up of quartz, feldspar, mica and hornblende.

Granite is commonly found in the base of statues and in kitchen countertops (once it’s polished).

Granite

1) Hardness (Mohs Hardness Scale)

2) Shape

3) Lustre

4) Colour

5) Streak

6) Cleavage & Fracture

Ways to Identify Minerals:

Frederick Mohs developed a scale in 1812 of ten minerals with a “hardness” value of 1-10.

This scale is used to identify different minerals based on its “scratchability”.

The Mohs Hardness Scale

Mineral Mineral Hardness Hardness of Common Objects

talc 1 (softest) Soft Pencil (1.5)

gypsum 2 Fingernail (2.5)

calcite 3 Piece of Copper (3.5)

fluorite 4 Iron Nail (4.5)

apatite 5 Glass (5.5)

feldspar 6 Steel File (6.5)

Quartz 7 Streak Plate (7)

Topaz 8 Sandpaper (7.5)

corundum 9 Emery Paper (9)

diamond 10

Mohs Hardness Scale:

At times minerals appear as crystals. Crystals occur naturally and they have straight

edges, flat sides and regular angles.

Minerals

All of the minerals (approx 3000) can be found in 1 of 6 crystal shapes.

Shapes of Minerals

Examples System Shape

Halite Cubic

Wulfenite Tetragonal

Corundum Hexagonal

Topaz Orthohombic

Gypsum Monoclinic

Albite Triclinic

Halite - Cubic

Mineral Examples and Shapes

Wulfenite – tetragonal

Mineral Examples and Shapes

Corundum – hexagonal

Mineral Examples and Shapes

Topaz – orthohombic

Mineral Examples and Shapes

Gypsum – monoclinic

Mineral Examples and Shapes

Albite – triclinic

Mineral Examples and Shapes

Lustre or “shininess” of a mineral depends on how light is reflected from its surfaceExample: Gold is a mineral that appears

shiny while others such as talc appear dull

Lustre:

Talc is a soft mineral. You can scratch it with your fingernail. It comes in many colors such as white, green, pink, and gray.

Color is one of the most attractive properties of minerals and offers clues into identifying them. Minerals are not always the same color all the

time. For example, the mineral Corundum is white/clear when it’s pure but when there is iron and/or titanium in it, the color is blue (and is called sapphire). When it contains chromium it’s red (and is called a ruby).

Colour:

Streak is the color that is left behind when a mineral is rubbed across a piece of an unglazed porcelain tile.For example: Gold leaves a yellow streak while

pyrite (often called fools gold) leaves a greenish-black or brown-black streak. Minerals harder than 7 on Mohs Hardness Scale will not leave a streak

Streak:

Cleavage and Fracture describe how the mineral breaks apart.

If a mineral breaks along smooth, flat surfaces or planes it is said to have cleavageMica is an example of a mineral with

cleavage

Cleavage & Fracture:

Some minerals are so rare and beautiful that they are very valuable such as diamonds.

Some common usages of diamonds: To make jewelry (rings, earrings, necklaces)On drill bits to cut through hard substances

such as steel and rockSurgical scalpels, razor blades, dental drills

and diamond coated computer parts

Uses of Minerals

Your body needs over 20 different elements found in minerals to survive. For example iron helps the blood carry oxygen.

Sodium (in small amounts) helps to regulate water in the body’s cells

Uses of Minerals

When a mineral breaks apart with rough jagged edges it is said to have fracture

Quartz is an example of a mineral with fracture

Other Clues to Mineral Identification