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Earth’s Surface Minerals & Rocks
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Minerals vs. Rocks A mineral is a solid formation that occurs naturally in the Earth. A rock is a solid combination of more than one mineral formations which is also occurring naturally.
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Characteristics of Minerals and Rocks
pure (made of same substance) more than one mineral some have crystals not single crystals usually pretty not usually as pretty usually have a shape no definite shape color is usually the same color is not the same no fossils some have fossils
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Applications of Minerals and Rocks
The commercial value of minerals is immense Rocks are mined to extract these minerals
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Rock Words mountain - huge, giant hunk of rock that is still attached to the earth's crust, doesn't move, tall boulder - large, taller than a person rock - large, you could get your arms around it or a bit smaller but it is usually jagged, broken off a bigger piece of rock river rock - round rocks that are along the edge & at the bottom of fast-flowing rivers stone - medium, you could hold it in two hands
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Rock Words pebble - small, you can hold it with two fingers, could get stuck in your shoe, usually rounded sand - made up of tiny pieces of rock, grains of sand grain - tiny, like a grain of rice or smaller, often found on a beach dust - really fine powder that is mixed in with sand or soil speck - as in a speck of dirt
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Minerals A mineral is the same all the way through. That is one reason we speak of a sample or a specimen rather than a rock. There are about 3000 known minerals on earth. All rocks are made up of 2 or more of these minerals.
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What is a Mineral? Naturally occurring Inorganic- not living Solid
Crystal Structure Definite chemical composition
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Properties of Minerals
Color– this varies depending on the chemicals present and is the least informative in identifying a mineral variety Luster – what the surface looks like in the light Specific Gravity– how heavy it feels Crystal Form – shape of crystal, shape the mineral would take if it had room to grow in a cavity
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Properties of Minerals
Cleavage– pattern when mineral is broken Fracture Tendency- toughness, how cohesive the mineral is, if it falls apart Hardness– what it can scratch & what scratches it Transparency - The ability to transmit light.
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Luster Determined by the intensity or quality of the light reflected by its surface
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Luster Metallic Glassy
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Luster Waxy/Greasy Pearly
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Luster Dull Silky
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Hardness Mohs hardness scale
Ranks ten minerals from softest to hardest Can be determined by a scratch test. A mineral can scratch any mineral softer than itself, but can be scratched by any mineral that is harder.
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Streak The color of its powder.
Color of a mineral may vary…its streak does not. Color of mineral and streak can often be different.
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Characteristics/Properties of Minerals
Naturally Occurring Inorganic Solid Crystal Structure Definite Chemical Composition
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Properties used to identify minerals
Color- provides little information Streak- color of mineral’s powder Luster- how light is reflected from a mineral’s suface Hardness- determined by a scratch test. Density- mass per unit of volume. Crystal Systems- Cleavage and Fracture
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Cleavage vs. fracture Cleavage Fracture
A mineral that splits easily along flat surfaces. Arrangement of the atoms causes it to break more easily in one direction How a mineral looks when it breaks apart in an irregular way. Quartz
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