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 make-up 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 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) Figure 1 A sample of granite, note the large crystals

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?