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Minerals CH 2 Prentice Hall p. 142 CH 2 Prentice Hall p. 142
What is a Mineral? A naturally occurring, inorganic solid that has a crystal structure and definite chemical composition. – Over 3,000 – 20 minerals form Earth’s crust. Rock forming minerals.
Naturally Occurring Must form through Earth’s geologic processes. – Cement, Brick, Steel and Glass all come from substances in Earth’s crust. – But they are manufactured by people.
Cannot come from materials that were once part of living things. – Coal- forms naturally, comes from the remains of plants and animals. Inorganic
Always solid, with a definite volume and shape. – Particles can’t flow freely. Solid
Crystal Structure Particles of a mineral line up in a repeating pattern. Forms a solid called a crystal. – Has flat sides called faces, that meet at sharp edges and corners.
A mineral always contains certain elements in definite proportions. Element- a substance composed of a single kind of atom. – All atoms of the same element have the same chemical and physical properties. Definite Chemical Composition
Compound- Two or more elements combined. – Most minerals are compounds. – Chemically joined. You can tell a compound by its chemical name like: NaCl for salt, CO2 for carbon dioxide Definite Chemical Composition
Mixture- consists of two or more substances that are mixed together but not chemically combined. (They can be sorted or seperated easily)
Color 1. Color is an easily observed physical property. Not the best property to use to identify because many minerals like quartz can come in a variety of colors. Identifying Minerals
Streak Streak is the color of the minerals powder when it is rubbed against a Streak Plate – This property does not vary like the color of the mineral can. Identifying Minerals
Luster Metallic luster- looks like a metal. Non-Metallic Luster- does not look like a metal, can be glassy, dull, earthy, waxy and pearly. Luster is used to describe how a mineral reflects light from its surface. Identifying Minerals
Crystal Structure Each mineral grows atom to atom to form that mineral’s particular structure. – Classified into six groups (crystal systems) based on the number and angle of the crystal faces. Identifying Minerals
5. Cleavage Cleavage- is a mineral that easily splits along flat surfaces. Identifying Minerals
6 Fracture Fracture- describes how a mineral looks when it breaks apart in an irregular way. Identifying Minerals
Special Properties Fluorescence- glows under UV (ultraviolet light) Fluorescence Magnetic- acts like a magnet Radioactive- give off radiation- Uraninite Reacts to Acid- reacts by fizzing. Electrical Properties- electric current can be produced (Quartz) – Used in watches Identifying Minerals
It is the mass in a given volume. It always remains the same for any given mineral. Density Identifying Minerals
A balance would be used to measure the mass of a sample. The sample can be placed in a graduated cylinder to determine the volume. Density Identifying Minerals
Water Displacement (how much water is moved, is equal to the volume of the sample) is used to determine the volume of the sample Density Identifying Minerals
One of the best clues. Mohs hardness scale. – A scale from 1 to 10. Hardness Identifying Minerals
Mohs Hardness Scale 10. Other Hardness’s 7.8.9. Can scratch steel and hard glass easily. Can scratch quartz.Can scratch topaz. 4.5.6. A steel nail can easily scratch it. A steel nail can scratch it.Cannot be scratched by a steel nail, but it can scratch window glass. 1.2.3. Softest known mineral. It flakes when scratched by a fingernail. A fingernail can easily scratch it. A fingernail cannot scratch it, but a copper penny can. Hardest known mineral, Diamond can scratch all other surfaces. Identifying Minerals