Minerals

Chapter 3-1Properties of Minerals.C. Welke

What is a mineral?Naturally occurringInorganicSolidCrystalline structureDefinite Chemical Composition

Naturally Occurring

Must be formed by a process in the natural world.

Not man made.

Inorganic

Can not be made of a material that was once part of a living thing.

Solid

Always has a definite volume and a definite shape.

Crystal Structure

Particles line up in a pattern that repeats over and over again.

The repeating pattern of a mineral’s particles form a solid called a crystal.

A crystal has flat sides called faces.

Definite Chemical Composition

Always contains the certain elements in definite proportions.

Almost all minerals are crystals.

Quartz is a compound of SiO2.

Some minerals are not compounds. Copper, Silver and Gold are pure solid elements of metals.

Identifying Minerals

Each mineral has characteristic properties that can be used to identify it.

Color Streak Luster Density Hardness Crystal Systems Cleavage and Fracture Special Properties

Color: Not mineral specific

Streak:The powdered form of a mineral

Streak

A streak test can help identify a mineral.

The streak of a mineral is the color of its powder.

Mineral color may vary but its streak will not vary.

Mineral color and streak color are often different.

Luster: How minerals reflect light

Non-metallic

Metallic

Luster can be:

Metallic Glassy Waxy, Greasy or

Pearly Submetallic or Dull Silky Earthy

Density

Each mineral has a characteristic density.

D=M/V Use a graduated

cylinder to get the volume of an irregular solid.

Hardness

Best clue to identify a mineral.

Is determined by a scratch test.

A mineral can scratch any mineral softer than itself, but can not be scratched by any mineral that is harder.

Hardness:Based on Moh’s scale of hardness

Crystal Systems

Grows atom by atom to form the minerals structure.

6 groups based on the number and angle of the crystal faces.

Crystals grown in open spaces can be perfectly formed.

Crystals grown in tight spaces can be imperfectly formed.

Crystal Systems

Shape a mineral takes if grown unimpeded

Mineral Java Applet

Cleavage

Splits easily along flat surfaces.

Fracture

Most minerals break apart in an irregular way.

Cleavage & Fracture

Best identified on a fracture surface

Other PropertiesFluorescence –

glows in the dark

Reactivity – reacts chemically to acid

Magnetism – naturally attracts metals

Optical Properties- bends light to produce a double image.

How Minerals Form

3-2

C. Welke

Crystallization

The process by which atoms are arranged to form a material with a crystal structure.

Can form in two ways by crystallization of molten material or by crystallization of materials dissolved in water.

Minerals From Magma and Lava Magma is molten

material from inside earth that hardens to form rock.

Cools slowly over many thousands of years.

Large Crystals

Lava is magma that reaches the Earth’s surface

Forms rock when it hardens and cools

Cool quickly and forms small crystals

Minerals From Solution: When elements and compounds that are dissolved in water

Minerals formed by evaporation When water

evaporates and leaves behind crystals

When ancient seas evaporated deposits of halite were left behind

Calcium and Gypsum are also formed this way

Minerals From Hot Water Solutions

Magma can heat underground water

The elements and compounds in the water leave the solution and crystallize when the water begins to cool

Water often flows in cracks in the rock layers

Veins occur when the water in between the rocks cool and leave behind metals or crystals

Using Mineral Resources

Chapter 3-3

Uses of Minerals

Minerals are the source of gemstones, metals, and a variety of materials used to make many products.

Gemstones: hard, colorful mineral that has a brilliant or glassy luster. Is durable and rare. Once cut and polished, it is called a gem. Used for jewelry, decoration, mechanical parts, and for grinding and polishing

Metals: Minerals such as aluminum, iron, copper or silver. Can be stretched, flattened or hammered. Are generally not as hard as gemstones

Uses for Minerals

Food Medicines Fertilizers Building Materials

Producing Metals From Minerals To produce metal from a mineral, a rock

containing the mineral, called an ore, must be located through prospection and mined, or removed from the ground. Then the rock must be processed to extract the metal.

Prospecting

Anyone who searches, or prospects, for an ore deposit

Mining: 3 Types of Mines

Strip Mines: earthmoving equipment scrapes away soil to expose the ore.

Open Pit Mining

Miners use giant earthmoving equipment to dig a tremendous pit and removing ore deposits.

Shaft Mines

A network of tunnels that extend deep into the ground, following the veins of ore

Smelting

The process of separating the metal in the ore from the other elements that are present in the ore.

Alloys

A solid mixture of 2 or more elements, at least one of them a metal.

Must have the characteristic properties of a metal.

Stainless Steel is an alloy.