Rocks & Minerals Minerals What is a Mineral? is a natural, nonliving solid with a definite chemical structure is a natural, nonliving solid with a definite chemical structure A mineral is a substance that must fit all parts of the definition A mineral is a substance that must fit all parts of the definition Natural Natural Nonliving solid Nonliving solid Definite chemical structure Definite chemical structure Are made up of crystals Are made up of crystals Partials of crystals are arranged in a particular, repeating pattern Partials of crystals are arranged in a particular, repeating pattern Naturally Occurring Formed by natural processes not in the laboratory Formed by natural processes not in the laboratory - Is an Ice Cube a mineral? - Is an Ice Cube a mineral? - Is the ice on the windshield of a car a - Is the ice on the windshield of a car a mineral? mineral? - Is copper a mineral? How Are Minerals Identified? Color Color Luster Luster Hardness Hardness Streak Streak Density Density Crystal Shape Crystal Shape Cleavage and Fracture Cleavage and Fracture Special Properties Special Properties Color Usually the first and most easily observed Usually the first and most easily observed -Some minerals are always the same color -Some minerals can have many colors QUARTZROSE QUARTZSMOKY QUARTZ Properties of Minerals Luster Luster The way a mineral reflects light. The way a mineral reflects light. Can be metallic or non-metallic. Can be metallic or non-metallic. Shiny or dull. Shiny or dull. waxy, pearly, glassy. waxy, pearly, glassy. This is a gem stone called tourmaline it has a glassy luster Hardness Resistance to scratching by different items; scratchability Resistance to scratching by different items; scratchability Mohs Hardness Scale >2 fingernail 3 penny 3 penny ~5 Steel of a pocket knife 5.5 Window Glass 6.6 Steel of a file 7 quartz crystal Properties of Minerals Streak Streak The color of its powder. The color of its powder. Not always the same as the color of the mineral. Not always the same as the color of the mineral. The mark it makes when rubbed against an unglazed tile The mark it makes when rubbed against an unglazed tile Properties of Minerals Density Density Minerals will have a certain density regardless of the size of the sample. Minerals will have a certain density regardless of the size of the sample. Each mineral has its own density called specific gravity Each mineral has its own density called specific gravity Crystal Shape Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming Cleavage and Fracture Cleavage is the tendency of a mineral to split or crack along parallel or flat planes Cleavage is the tendency of a mineral to split or crack along parallel or flat planes Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes. Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes. BIOTITE QUARTZ Obsidian No Cleavage 1 Direction of CleavageConchoidal Fracture Mohs Mineral Hardness Scale 1) Talc 2) Gypsum 3) Calcite 4) Flourite 5) Apatite 6) Feldspar 7) Quartz 8) Topaz 9) Corundum 10) Diamond Softest Hardest Rocks Rocks classification Texture Texture Grain Grain Minerals Minerals Color Color Origin of rocks Origin of rocks Rock classification Texture is how a rock looks and feels Texture is how a rock looks and feels texture in rocks is determined by the size, shape, and pattern of a rocks grains. texture in rocks is determined by the size, shape, and pattern of a rocks grains. ocal.wasp.uwa.edu.au/.../rock/rock16.jpeg Rock Classification Grain Grain Size -- large, small Shape --smooth, rough, round jagged Pattern rows, waves, swirls, beads or random patterns Rock classification Mineral composition Mineral composition Rocks are made of more than one mineral blue.utb.edu/.../PHYS1417SPR00/Unit3Lec.html Rock Classification Origin of rocks Origin of rocks How were the rocks formed How were the rocks formed - magma - magma - erosion and layering - erosion and layering - heat and pressure - heat and pressure Origin of rocks Sedimentary rocks are formed from other rocks that are broken into small particles and moved by erosion (wind or water) Sedimentary rocks are formed from other rocks that are broken into small particles and moved by erosion (wind or water) The particles are squeezed or cemented together The particles are squeezed or cemented together Rocks are layered Rocks are layered Origin of rocks Igneous rocks are formed from the cooling of magma or lava Igneous rocks are formed from the cooling of magma or lava Lava is magma that reaches the earths surface Origin of rocks Metamorphic rocks are formed from other rocks Metamorphic rocks are formed from other rocks Rocks have been pushed deep into the earths crust Rocks have been pushed deep into the earths crust Pressure from the earth above and heat from the mantle below cause them to change shape, color, grain and crystal structure Pressure from the earth above and heat from the mantle below cause them to change shape, color, grain and crystal structure07page01.cfm?chapter_no=visualization Rock cycleons/es0602/es0602page02.cfm Clues to the Past Rocks have clues to that tell us about past events Rocks have clues to that tell us about past events Scientetist can look at rocks especially sedimentary rocks because they form in layers. Scientetist can look at rocks especially sedimentary rocks because they form in layers. The oldest layers are on the bottom The oldest layers are on the bottom Relative dating lets scientist place past events in sequential order Relative dating lets scientist place past events in sequential order Clues to the Past The Grand Canyon was formed 5 million years ago when the Colorado River cut through the sedimentary rocks. This provides a great deal of information about Earths History The Grand Canyon was formed 5 million years ago when the Colorado River cut through the sedimentary rocks. This provides a great deal of information about Earths History Fossils Fossils can form when an organism is buried in soft mud Fossils can form when an organism is buried in soft mud Most Fossils form from hard parts like bones, shells, or wood. Most Fossils form from hard parts like bones, shells, or wood. Burrows and footprints can also be fossilized. Burrows and footprints can also be fossilized. Many fossils were made by species that are now extinct. Many fossils were made by species that are now extinct. Fossils can help scientist determine the rocks age Fossils can help scientist determine the rocks age Why is Soil important to living things Weathering is when weather, water and living things break down rocks and create soil. Weathering is when weather, water and living things break down rocks and create soil. Weathering takes place over many years. Weathering takes place over many years. What makes up soil? Rock Rock Clay Clay Silt Silt Sand Sand Humus Humus 3 Layers of Soil: topsoil, subsoil and bedrock What is topsoil? Topsoil is the upper surface of soil. Topsoil is the upper surface of soil. It is a natural product of subsoil and bedrock. It is a natural product of subsoil and bedrock. Topsoil is the best for plant growth. Topsoil is the best for plant growth. What is Subsoil and Bedrock? Subsoil and bedrock are layers of soil under the topsoil that are formed over a long period of time by water. Subsoil and bedrock are layers of soil under the topsoil that are formed over a long period of time by water. Subsoil and bedrock arent as good for growing plants as topsoil Subsoil and bedrock arent as good for growing plants as topsoil What is Humus? (HYOO-mus) Humus is decayed or dead matter in soil. Humus is decayed or dead matter in soil. It adds nutrients to the soil. It adds nutrients to the soil. Humus is found in topsoil. Humus is found in topsoil. What is Clay? Clay contains small particles of soil that hold water well and provides nutrients. Clay contains small particles of soil that hold water well and provides nutrients. What is Sand? Sand is made up of small grains of worn- down rock. Sand is made up of small grains of worn- down rock. It has few nutrients. It has few nutrients. Sand doesnt hold water well Sand doesnt hold water well What is Silt? Silt is composed (made up of) very small broken pieces of rock. Silt is composed (made up of) very small broken pieces of rock. Its particles are larger than clay and smaller than sand. Its particles are larger than clay and smaller than sand.