Earth Science Chapter 3 Minerals Section 1 Minerals

Earth Science - Chapter 3 Minerals

Section 1 • Minerals – Four properties – Naturally Occurring – Formed by processes on or inside the earth with no input from humans – Inorganic – not made by a life process – Defined Chemical Composition – Fixed makeup of elements or compounds – Atoms have an orderly arrangement which leads to the crystalline structure

Section 1… Continued • Crystal – Solid with atoms arranged in orderly, repeating patterns – Some crystals form from magma – a hot melted rock below the Earth’s surface • Slow Cooling – creates large crystals • Fast Cooling – creates small crystals • Example: Volcano erupts and on the slop of the hill you will have larger crystals forming in comparison to those cooled quickly by the sea

Slow vs Fast Cooling Figure 1 A sample of granite, note the large crystals Figure 2 A sample of rhyolite - the crystals are too small to see. (The colour banding was produced as the sticky lava flowed over the ground)

Crystals… Continued • Crystals can also be formed by solutions evaporating – Elements with in the solution form crystals as the volume of liquid is reduced – The dissolved particles form crystals as a result – Example: Rock Candy - sugar

Section 1… Continued • Mineral groups – have the same composition throughout – Silicates are the largest group of crystalline structures • Silicon and oxygen are the two most abundant elements in Earth’s crust; they form the building blocks of many minerals.

Section 2 – Mineral Identification • Color and Appearance are not enough information to distinguish one mineral from another • Hardness is a measure of how easily a mineral can be scratched; The Mohs scale compares minerals hardness – Softest – a fingernail scratch…Talc – Hardest – can not be scratched… Diamond

Section 2 - Continued • The way a mineral reflects light is its luster – Can be metallic or nonmetallic – Nonmetallic lusters include • • Dull Pearly Silky Glassy • Specific Gravity is the ratio of the mineral’s weight to the weight of an equal volume of water.

Section 2 - Continued • Streak is the color of the mineral in powder form. – Note… the mineral must be softer than the porcelain plate that is used in the test • The way in which a mineral breaks apart can be a distinguishing characteristic. – Minerals with cleavage breaks along smooth, flat surfaces – Minerals with fracture break with uneven, rough, or jagged edges

Section 2 - Continued • Other minerals have very unique properties like how light passes through them or magnetism

Section 3 – Uses of Minerals • Gems are rare and beautiful minerals that are highly prized – The Hope diamond and the Cullinan diamond are famous historical gems – Gems also have industrial applications. • Abrasives • Lasers • Electronics

Section 3 - Continued • Minerals can be mined for the elements they contain – An ore is a mineral or rock containing a substance that can be mined for profit – Elements must be refined, or purified, from the ore – Elements that can be dissolved in liquids can sometimes travel to and pool in cracks of rocks. These are called veins.

Section 3 - Continued • Mineral combinations are very helpful as well. – Titanium is a useful metal that comes from the combination of two minerals, ilmenite and rutile

Discussion Questions • How does the rate of evaporation effect crystal shape? • How does the rate of evaporation effect crystal size? • Name five properties that can be used to identify a mineral. • Besides jewelry, what are some other applications for minerals?