Geology

Rocks, Minerals, Volcanoes, & Earthquakes

Minerals

Naturally occurring Inorganic solid ( not from living

matter)Has a definite structure; crystalsHas a definite composition; a

compound or element.

Minerals

Crystals =is a solid in which atoms are arranged in repeating patterns.

NaCl, table salt , forms a cubic crystal. Wulfenite forms a tetragonal crystal. Corundum = Hexagonal Gypsum = Monoclinic Topaz = Orthorhombic

Topaz

Mineral : How they form…

1. Hot magma ( melted rock) cools to form minerals.

The types and amounts of elements in the magma determines which minerals form.

2. Crystals form from minerals dissolved in liquids.

When the liquid evaporates, mineral crystals are left behind.

How Minerals Form:

3. Precipitation out of solution is the third way.

Mineral Composition There are 90 elements that occur naturally;

98% of the Earth’s crust is made of only eight of these elements.

Oxygen is 46.6% Silicon is 27.7% Aluminum is 8.1% Iron is 5% Calcium is 3.6% Sodium is 2.8% Potassium is 2.6% Magnesium is 2.1%

Mineral Groups

There are about 4000 minerals. Most of the common minerals are in the

group called silicates. Silicates contain silicon, oxygen and

one or more other elements. Quartz and Feldspar are common

rock-forming minerals in the silicate group.

Feldspar

Quartz

Mineral Groups

Carbonates Oxides Sulfides Sulfates Halides Hydroxides Phosphates

Mineral Identification Appearance Hardness Luster Color Streak Fracture Cleavage Other Properties

Mineral Properties Appearance – Color and general

appearance can help to identify a mineral.

Many minerals look very similar. Many minerals are found in different

colors.

Other properties must be used to identify minerals.

Mineral Properties

Hardness = The Mohs Scale of Hardness measures how easily a mineral can be scratched.

Talc is the softest, a 1 on the scale. Diamonds are the hardest, a 10.

Talc

Mineral Properties: Hardness

Mohs Scale

Mineral Properties:Luster

Luster: how light is reflected from a mineral’s surface.

Metallic Luster = shines like metal Nonmetallic Luster = any mineral that

does not shine like metal. Nonmetallic can be : dull, pearly, or

silky.Orthoclase

Galena

Luster

Mineral Properties: Streak Streak is the color of the mineral when it

is broken up and powdered. The mineral is rubbed across a white,

unglazed, porcelain tile. Minerals harder than the streak plate (7)

will not have streak. Graphite (pure carbon) has streak on

paper. It is used in pencils, not lead.

Mineral Properties: Cleavage and Fracture Minerals that break with rough or jagged

edges have fracture. Minerals that break along smooth , flat

surfaces have Cleavage. Some minerals have unique

properties; Magnetite is magnetic, Calcite fizzes

with HCl ( acid).

Mineral Properties: fracture

21.Limestone = even 22. Serpentine = uneven 23. Obsidian = conchoidal 24. Rose Quartz = sub-conchoidal 25. Tremolite = splintery 26. Copper = hackly

Types of Cleavage

Mineral Properties: Cleavage

15. Mica = Basal ( one direction) 16. Feldspar = Pinacoidal ( two

directions)

17. Amphibole = Prismatic ( Two directions at 124o and 56o

Cleavage

18. Halite = Cubic ( Three directions, at right angles)

19. Calcite = Rhombohedral ( Three directions not at right angles.)

20. Fluorite = Octahedral ( four directions)

Uses of Minerals Jewelry on the Web

Gems are rare and beautiful minerals which are cut and polished for jewelry.

Differences between gems and common minerals are small: Amethyst is a gem form of quartz (SiO2) with manganese traces. The Mn gives amethyst its purple color.

Uses of Minerals Ores is a mineral that is useful, and can

be mined for profit. Bauxite is a mineral ore used to make

aluminum.

Hematite is a mineral ore source for iron.

Uses For mineralsMinerals in Your House(Web)

Copper is used for coins, wires, pipes and cooking tools.

Ilmenite and rutile are mineral ores which provide titanium. It is used for hip replacements, bicycles, and airplane parts

Science and Art

Minerals are in paint pigments, crayons, pastels, chalks, clays, and glazes.

Cinnabar is used for red. Malachite and Azurite are used for

greens and blues.

By Salvador Dali

Science and Art

Lapis Lazuli is used for dark blues. Ochre is used for yellows and reds

By Salvador Dali