Learning Objective Identify minerals by observing their physical
Learning Objective: Identify minerals by observing their physical properties.
Think-Pair-Share What is a mineral?
What is a mineral? -A mineral is any naturally-occurring, inorganic, homogeneous solid that has a definite chemical composition and a distinctive internal crystal structure -Minerals are solid substances in which atoms are arranged in an orderly, threedimensional pattern -All rocks are made up of minerals.
Elements found in minerals and rocks Eight elements combine to make most minerals and rocks found in the Earth's crust. These elements are oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
How can you distinguish one mineral from another? As we mentioned earlier, each mineral has a specific, unique chemical composition and three-dimensional pattern. Physical properties can be used to identify a mineral
Learning Objective: Explain the 5 physical properties of minerals by reading a science text and completing a tree map.
Elements and Compounds All minerals are either elements or compounds. Not all elements and compounds are minerals. Na (sodium) = gray metallic clay Cl (chlorine) = yellow-green gas Na. Cl (salt) = white crystal ( mineral Halite)
Periodic Table of Elements All minerals are made up of elements
Crystal Structure-regular repeating pattern and arrangement of atoms Atoms are the smallest unit of any element.
Definite Chemical Composition A mineral is made of the same material throughout; same ratio of elements; the chemical formula is definite Examples C Diamond Na. Cl Halite
Homogenous Material is distributed evenly throughout.
Occur naturally & Inorganic Occur naturally - minerals form by natural geologic processes. Inorganic- not made out of anything living (plants or animals).
A few minerals, such as diamond, graphite, gold and sulfur are made up entirely of one element. Diamond (C) Most minerals are a combination of two or more elements that are chemically combined. Pyrite(Fe. S 2)
Rocks & Minerals are the building blocks of rocks. A mineral must meet every characteristic (listed on previous slide), otherwise it is a rock
Physical Properties of Minerals During the remainder of the lesson, as well as our laboratory exercise, we will focus on the physical properties of minerals and the various mineral identification tests that are commonly used to distinguish one mineral from another. The physical properties most commonly used in mineral identification are: 1) Color 2) Streak 3) Luster 4) Cleavage 5) Hardness
Color is one of the most obvious physical properties, but is LEAST helpful in determining a mineral Why? ?
Fluorite is one example of a mineral that has many color variations. Due to the differences in color, other physical properties must be examined in order to determine whether a given specimen is Fluorite, or simply another mineral of the same color.
Streak Refers to the color of a mineral when it is powdered Better than using color in solid form Commonly obtained by rubbing the mineral across the surface of a streak plate
Luster refers to the way a mineral reflects light. Minerals that look like metal have metallic luster while those that do not have non-metallic luster: Metallic luster: shiny, opaque appearance Non-metallic: dull, silky, glassy, earthy, waxy or translucent.
Metallic Luster vs. Nonmetallic Luster Notice how Pyrite is shiny and metallic looking, with an appearance similar to that of a bright chrome bumper on an automobile.
Cleavage vs. Fracture Cleavage and Fracture are minerals properties that describe the way a mineral breaks when stressed. Depending on the internal arrangement of atoms, different minerals fracture, or break, in different ways Cleavage- minerals that break into distinct planar surfaces (flat surfaces) have cleavage. Fracture- When these minerals are stressed they shatter making no two pieces truly the same. -If minerals do not have cleavage they have fracture instead.
Some minerals have no cleavage, some have one direction of cleavage while others have two or three that intersect at a specific angle.
Hardness A measure of the relative ability of a mineral to resist scratching Representative of the resistance of bonds in the crystal structure to being broken Diamond is the hardest mineral while talc is one of the softest.
Mohs Hardness Scale Lists some minerals in order of relative harness Ranges from 1 to 10, with 1 being the softest (Talc) and 10 the hardest (Diamond) A mineral will scratch any mineral that has a hardness less than itself If a mineral cannot be scratched by another mineral it must have a hardness that is greater than that mineral. Ex: A mineral with a hardness of 5 can scratch all minerals with a hardness of 5 or less
Measuring hardness When testing a mineral-if you can scratch it with your fingernail (hardness of 2. 5) it must have a hardness less than 2. 5. If the mineral is able to scratch the glass plate (hardness of 5. 5) it must have a hardness greater than 5. 5 If the mineral does not scratch with your fingernail and does not scratch the glass plate, it must have a hardness between 2. 5 and 5. 5.
Independent & Group Work Use your checklist for each mineral to check off any of the physical properties your mineral sample has. When you are finished, use the classification chart to identify each mineral with a letter. I will come around and tell you the name of the mineral. When you are finished, begin working on the analysis questions. Extension- identify the names of the minerals and move on to identifying the additional samples.
Analysis Questions 1. Explain why color is an unreliable clue to the identity of a mineral. 2. Summarize how you would determine the hardness of an unidentified mineral sample. 3. How does cleavage differ from fracture? 4. Is Ice a mineral? (Hint-it has a crystalline structure). Explain your answer.
Share-Out & Reflection Let’s share out the answers to the mineral identification. Let’s share out the answers to the analysis questions. Explain how can we distinguish one mineral from another?
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