Minerals Section 4.1

Why Are Mineral’s Important? “Minerals play important roles in forming rocks…and continue to play a role in shaping civilization” -Calcite is the mineral that forms the 2 million limestone blocks that make up the Great Pyramid in Egypt. -Wars have been fought and empires have crumbled over minerals such s gold and silver.

Quick History Lesson http://www.youtube.com/watch?v=rjhIzemLdos

What is A Mineral? How are they different from rocks? A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure. A rock is a naturally occurring aggregate of minerals and/or mineraloids. Rocks do not have a definite chemical composition. For example: Gabbro has plagiocase, pyroxene, olivine (all minerals).

What Do You Mean Naturally Occurring? It mean’s cannot be created in a lab. That means synthetic diamonds that are created in a lab cannot be minerals. Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle.

Mineral Characteristics (Slide 1) All minerals are naturally occurring by natural processes. Substances created in a lab are not minerals. Second, all minerals are inorganic. That is, they aren’t alive and never were during their existence. (Let’s talk about coal).

Coal Does Not Fit. Why?  Coal is formed by ancient plants and animals accumulating in moist peat bogs. As plants die off in a wet area, they pile up into peat. It takes between 4,000 and 100,000 years for one meter of peat to accumulate. This process happens best in river deltas or coastal plains. Over time, these peat seams are compressed by further deposits and the carbon content of the coal is concentrated. The older the coal gets, generally, the harder and blacker it gets.

Mineral Characteristic’s (Slide 2) Solid’s With Specific Compositions -Quartz -Solids have definite shapes, gas and liquids do not. -Each type of mineral has a chemical composition unique to the mineral. Most consists of a combination of elements, while others (like Silver) are composed of a single element. A combination of two oxygen atoms and one atom of silicone.

Mineral Characteristics (Slide 3) Definite Crystalline Structure The atoms in minerals are arranged in geometric patterns that are repeated over and over again. Unfortunately, well defined crystal shapes shown in the examples are very rare. Why? Most minerals are formed in restricted spaces.

Crystal Systems

Important Mineral Groups To Know Silicates: Oxygen is the most abundant element in earth’s crust, followed by silicon Minerals that contain silicon and oxygen (and other elements) are known as silicates. Examples are Quartz and Feldspar. Carbonates: Carbonates are minerals composed of one or more metallic elements with the carbonate compound CO3 Oxides: Oxides are compounds of oxygen and a metal. Hematite (Fe2O3) and Magnetite (Fe3O4) are examples of oxides.

Elements In Earth’s Crust

End of Section 4.1

Minerals Section 4.2

Mineral Identification Geologist rely on several simple test to identify the minerals. Color: Most noticeable characteristic, but the least reliable to use on it’s own. To many variables to depend totally on color. Luster: The way light reflects on a mineral is called luster. Luster is described as metallic and non-metallic. Silver, gold, copper, etc have shiny surfaces. Non-metallic minerals, such as calcite, gypsum, and sulfur do not.

Mineral Identification Texture: Describes how a mineral feels to touch. Smooth, rough, ragged, rusty, etc. Also rarely used on it’s own. Streak: Is the color of a mineral when it is broken up and powdered. Hardness: Is a measure of how easily a mineral can be scratched on of the most useful ways to identify a mineral. Cleavage: Minerals break along planes where atomic bonding is weak. (Will go over in the video).

Mineral Identification Density and Specific Gravity (Will not be included on any test): Give the pyrite and gold example on the board. Density is the mass of the substance divided by the volume. Specific Gravity is the ratio of the weight of a substance to the weight of an equal volume at water at 4 (celcius)

Mineral Identification Video http://www.youtube.com/watch?v=c7wJP_K_sAQ

End of Chapter 4/ Final Question How can minerals be used for human use? Give some examples.