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3.1 The Rock Cycle !

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3.1 Rock Cycle Interactions among water, air, and land can cause rocks to change from one type to another. The continuous processes that cause rocks to change make up the ROCK CYCLE. Main Idea: Rocks get around and recycle!

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3.1 The Rock Cycle Shows the interrelationships among the three rock types (igneous, sedimentary, and metamorphic) Magma is molten material that forms deep beneath the Earths surface. Lava is magma that reaches the surface. Weathering is a process in which rocks are broken down by water, air, and living things. Sediment is weathered pieces of Earth elements.

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3.1 Rock Cycle

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The difference between the three types of rocks (igneous, metamorphic and sedimentary) is: how the rocks are formed!!! 3.1 Rock Cycle

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Igneous Rocks Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Igneous comes from the Latin word for fire. 3.1 Rock Cycle: Rock Types

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Igneous rock that cools inside the earth is called intrusive igneous rock. Intrusive igneous rock cools slowly which gives it time for crystals to form. 3.1 Rock Cycle: Rock Types Igneous Rocks

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Examples of intrusive igneous rock. Granite is the most common intrusive igneous rock. 3.1 Rock Cycle: Rock Types

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Igneous rock that cools on the earths surface is called extrusive igneous rock. Extrusive igneous rock cools quickly. If air bubbles are trapped in the rock during cooling, the rock can have a rough surface. If it cools very quickly, the surface can be smooth like glass! 3.1 Rock Cycle: Rock Types

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Examples of Extrusive Igneous Obsidian is volcanic glass. Basalt is another example. Pumice is another example. 3.1 Rock Cycle: Rock Types

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Sedimentary Rock Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. 3.1 Rock Cycle: Rock Types

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The sediment is generated when these materials are weathered. Weathering is the process of breaking larger materials into smaller fragments. 3.1 Rock Cycle: Rock Types Sedimentary Rock

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What weathered this rock?

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Gradually, the sediment accumulates in layers and over a long period of time (and with pressure) hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. Sedimentary Rock 3.1 Rock Cycle: Rock Types S O F T !

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Limestone (sedimentary)

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Metamorphic Rock Metamorphic rocks are formed under the surface of the earth (from meta=change; morpho=form). Metamorphic rock is either igneous or sedimentary rock that (under incredible pressure and heat) gets baked. This pressure and heat rearranges the atoms of the mineral. 3.1 Rock Cycle: Rock Types UNDER PRESSURE!

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So.. The chemical composition of a metamorphic rock will be the same as another rock, but the atoms will be rearranged. Metamorphic Rock

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Metamorphic Rock Example Limestone is sedimentary calcium carbonate. Marble is metamorphic calcium carbonate.

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From Sedimentary to Metamorphic Shale is sedimentary rock. Slate is metamorphic shale.

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Rock Cycle Summary

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Characteristics of Minerals and Rocks!

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Minerals are defined by their physical and chemical properties. There are several common characteristics that we will use in our rock lab. Now we will explore each of these characteristics.

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Physical Property: Color Definition: The visible light that is reflected by the mineral. Testing Method: Look at the sample and determine its color - white, black, green, clear, etc.

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Physical Property: Crystal Form Definition: Geometric shape of a crystal or mineral. Testing Method: Examine and describe the geometric shape of the mineral - cubic, hexagonal, etc. Not commonly seen in most introductory lab samples.

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Physical Property: Cleavage Definition: Breakage of a mineral along planes of weakness in the crystal structure. Testing Method: Examine the mineral for areas where the mineral is broken. Look for areas where the light reflects from planar surfaces. This can be easily confused with a crystal face and is the most difficult properties for students to master.

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Physical Property: Hardness Definition: Resistance to scratching or abrasion. Testing Method: Use minerals of known hardness from the Mohs Hardness Kits. Scratch the unknown mineral with a known hardness to determine which mineral is harder. Continue doing this with harder or softer minerals from the kit until the hardness is determined (using the scale).

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Physical Property: Luster Definition: Character of the light reflected by a mineral. Testing Method: Look at the sample to determine if the mineral is metallic in appearance (looks like a chunk of metal) or non-metallic (doesn't look like a chunk of metal).

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There are two types of luster: metallic and non- metallic.

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Physical Property: Magnetism Definition: Electromagnetic force generated by an object or electrical field. Testing Method: Use a magnet to determine if the magnet is attracted to the sample.

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Magnetite (Fe 3 O 4 )

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Physical Property: Reaction to HCl Definition: Chemical interaction of hydrochloric acid and calcium carbonate (CaCO 3 ). Testing Method: Place one small drop of HCl on a sample a watch for a reaction - effervesces (bubbles).

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Physical Property: Streak Definition: Color of the mineral when it is powdered. Testing Method: Grind a small amount of a mineral into a powder on a porcelain streak plate and determine the color of the powder.

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Physical Property: Other Properties Definition: Fluorescence, Radioactivity Testing Method: Requires special equipment such as a UV lamp and Geiger counter. These are not commonly tested for in an introductory lab.

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Mineral fluorescence takes place when the incoming ultraviolet energy is absorbed by a mineral and is immediately given off as visible light. With regular visible light. Under ultraviolet light.

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Another Fluorescent Mineral

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Radioactivity is another special property

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Pitchblende (uranium)

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Lets Review!!!

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1. The color of the powder left behind when the mineral is scraped across a surface Streak 2. The way in which light reflects from a minerals surface Luster 3. The tendency of a mineral to break along flat surfaces Cleavage 4. The tendency of a mineral to break into irregular pieces Fracture 5. The visible light that reflects off the mineral Color 6. The ability of a mineral to attract a magnet. Magnetism 7. The reaction of acid on the mineral Reaction to HCl/Solubility 8. The light that shines when ultraviolet is shined on a mineral. Fluorescence 9. A minerals resistance to being scratched Hardness

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Gems

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Gem Minerals Diamond Diamond forms at great depths within the lithosphere, where pressures are in excess of 200 kilobars and temperatures of 800 C or higher. Due to its hardness and resistance to acids ancient Greeks called it adamas meaning the invincible. The rock in which diamonds occur is kimberlite (metamorphosed pegmatite) found in areas of Siberia, South Africa, India, Zaire, Australia, etc. Most commonly diamonds are found in alluvial deposits, but also mined directly from kimberlite (diamond pipes). Less than 25 % of total worlds production of diamonds is suitable for gems. The value of diamonds depends on the four Cs: color, clarity, cut, and carat weight. The most valuable are colorless and blue-white stones. The worlds largest diamond is Cullinan, found in South Africa in 1905. Cullinan weighs 3106 carats (1 carat = 0.2 grams). First diamonds were synthesized in 1955 in the United States. Diamond Emerald Emerald is green color variety of silicate mineral beryl. Most commonly it occurs in igneous rocks (pegmatite and granite) but also in metamorphic rocks (mica schists). The most valuable emeralds are found in Colombia. Other areas of significant emerald production are South Africa, Zimbabwe, and Russia. Emerald is often considered more valuable than diamond. Emerald Ruby Ruby is red color variety of oxide mineral corundum. It occurs in metamorphic rocks (marble, gneiss, mica schist) but also in silica deficient igneous rocks such as siyenites. Name of the gem was derived from Latin ruber, meaning red. The most valuable rubies have deep red color, known as a pigeon-blood, and seldom are larger than three carats. The finest Mogok rubies come from Myanmar (Burma). Other areas include Tailand, Cambodia, Sri Lanka, Kenya, etc. Ruby Sapphire From Latin sapphirus, meaning blue; blue variety of corundum. Sapphires are much more abundant, thus less valuable than rubies. Some of the largest samples exceed 100 carats. The most highly prized are cornflower-blue stones from Cambodia found in alluvial deposits. Other areas of significant production are Tailand, Sri Lanka, India, and Australia. Semiprecious gems: Sapphire Pearl One of the oldest known gems. Certain species of saltwater oysters and freshwater clams build concentric layers of aragonite around sand that penetrates their epithelum (mantle). Pearls may grow flat (blister pearls), irregular (baroque pearls), but most valuable are spherical or drop like pearls. The color of pearls varies with the mollusk species and water environment. The most valuable are rose Indian pearls. Other colors are cream (Persian Gulf and Japan), white with greenish and bluish shades (Australia), black and reddish-brown (Mexico), golden-brown (Panama) etc. The value of natural pearls significantly decreased after huge quantities of cultivated pearls invaded the world market. Pearl Amber Amber is a hardened resin of coniferous trees, usually yellowish brown, but occasionally deep brown to red, green, or blue. Trapped insects, air bubbles, and dust particles may be found in some specimens. The most abundant amber particles are found along the shores of the Baltic Sea, along the coast of Sicily, and Myanmar (Burma). Amber Coral Marine organisms that live in large colonies in shallow, warm, and clear seas. Their skeletal parts precipitate as aragonite and calcite in many different colors and shapes. The most sought are branch-like corals in red, reddish-rose colors (Mediterranean off the coast of Algeria) and black horn-like corals (Hawaii). Coral