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”

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

• -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.

-Quartz• 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

Color• Color is sometimes caused by

the presence of trace elements or compounds within a mineral.

• Quartz can be found in a variety of colors because of different trace elements. For example purple amethyst contains ferric iron.

• Color least reliable diagnostic test. The same mineral can have a variety of minerals, have impurities, or be affected by weathering.

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.

Texture

• Texture: Describes how a mineral feels to touch. Smooth, rough, ragged, rusty, etc. This diagnostic test is also rarely used on it’s own in the field.

Streak

• Streak: Is the color of a mineral when it is broken up and powdered.

• For example, pyrite, which is also known as fool’s gold, leaves a greenish back streak.

• A mineral’s streak is rarely changed even when it’s weathered.

Hardness

• Hardness: Is a measure of how easily a mineral can be scratched.

• For example, Talc is one of the softest minerals and can be scratched by a fingernail.

• In contrast, diamond can be used as a sharpener and a cutting tool.

• Great diagnostic tool. Not affected by weathering or impurities.

Cleavage

• Cleavage: Minerals break along planes where atomic bonding is weak.

• Mica has perfect cleavage that breaks long planes where atomic bonding is weak. Quartz breaks unevenly among jagged edges because of the tightly bonded atoms.

Density and Specific Gravity • Density is the mass of the

substance divided by the volume.

• In the field, it is difficult distinguish density differences by lifting two comparable minerals. That is why we do a specific gravity test.

• Specific Gravity is the ratio of the weight of a substance to the weight of an equal volume at water at 4 (celcius)

Special Properties

• Some minerals have unique special properties.

• Iceland Spar: Light is bent in two different directions. The refractions creates the appearance of two images.

• Calcite: Fizzes when it comes into contact with hydrochloric acid (HCl)

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.