Mineral Identification Minerals can be identified by a

Mineral Identification Minerals can be identified by a combination of their physical properties (characteristics).

COLOR ØSome minerals come in more than one color. Ex. Quartz

Ø Some different minerals have similar colors. Ex. Fluorite and Amethyst Quartz

LUSTER Ø Definition: How a mineral reflects light. Ø Luster can be divided into two categories: Ø A. Metallic- Shines like a metal 1. metallic shiny – ex. Graphite and Galena

Metallic Luster Ø 2. Metallic Dull- looks more like a rusty nail

LUSTER NON-METALLIC- doesn’t shine like a metal 1. Glassy luster ex. Quartz B.

Non-metallic luster Ø 2. Pearly- shine like a pearl ex. Talc

Non-metallic luster Ø 3. Silky luster- shines like corn silk ex. Gypsum

Non-metallic Luster 4. Waxy luster- shines like candle wax ex. Some Quartz and some Halite

Non-metallic Luster Ø 5. Earthy Luster- “shines” like dirt ex. Bauxite

Non-metallic luster Ø 6. Resinous Luster- shines like sticky honey or amber ex. Sphalerite

Ø One kind of mineral can have two different forms and so it may have two types of luster. ex. Hematite- it may be Specular Hematite which is metallic-shiny, or it can look metallic-dull

Mini Lab Ø 1. Get a tray -divide the minerals in to two groups: metallic and nonmetallic Ø 2. Divide the metallic minerals in to two groups: shiny and dull metallic Ø 3. Group the nonmetallic minerals by glassy, pearly, silky, waxy, earthy, and resinous luster

STREAK Ø Streak-color of a mineral’s powder when scratched on an unglazed porcelain tile called a streak plate Ø Not all minerals leave a streak!

HARDNESS Ø Hardness- a mineral’s resistance to being scratched Ø Friedrich Mohs invented Mohs Scale of Hardness Ø Diamond- hardest mineral; Talc softest mineral

MOHS SCALE OF HARDNESS 10 9 8 7 6 5 4 3 2 1 Diamond – the hardest mineral Corundum Topaz Quartz Orthoclase (Feldspar) Apatite Fluorite Calcite Gypsum Talc – represents the softest mineral

MNEMONIC DEVICE Ø To learn Mohs Scale of Hardness, memorize the following sentence: Ø “To Get Candy From Aunt Fanny, Quit Teasing Cousin Danny. ” Ø Did you notice that the first letter of each word in the sentence corresponds to the first letter of each word in Mohs Scale? This is a mnemonic device (memory aid)

MOHS SCALE OF HARDNESS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Talc (softest) Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond (Hardest) To Get Candy From Aunt Fanny Quit Teasing Cousin Danny

COMMON OBJECTS TO HELP TEST MINERAL HARDNESS The following objects can be used to help determine the hardness of a mineral: Ø Fingernail –Hardness of 2. 5 Ø Copper Penny- H: 3. 1 Ø Iron Nail – H: 4. 5 Ø Ø Glass Plate – H: 5. 5 Steel File – H: 6. 5 Streak Plate – H: 7. 0

Mini Lab Ø Divide the minerals into metallic and nonmetallic luster and check with teacher Ø Check the streak of the metallic and nonmetallic minerals and tell your teacher what you found out (AHA!!) Ø Take the nonmetallic minerals and line them up by hardness using tools and the minerals themselves to help you! Ø Memorize Moh’s Scale for a quiz next week

CLEAVAGE Ø Cleavage- the way a mineral may split easily along flat surfaces

Planes of weakness Ø Ex. ) Halite has an atomic structure that forms cubic breakage

Geologists use hammers and knives to determine how a mineral breaks

Minerals may have very distinctive cleavage Ø Mica-one direction of perfect cleavage. Ø Calcite (rhombic) and Galena (cubic)- cleavages in 3 directions.

Cleavage can be observed under a microscope in a thin section

FRACTURE Ø Fracture -the way a mineral breaks unevenly, not with smooth, flat surfaces Ø Examples: Ø a. Conchoidal fracture -a curved, shelllike pattern, like broken glass; ex. Quartz

OTHER FRACTURE PATTERNS Ø b. Fibrous fracture looks splintery. Ex. Gypsum and Asbestos

MORE FRACTURE PATTERNS Ø c. Irregular or uneven fracture- shows no definite pattern; ex. Hematite and Magnetite

CRYSTAL SHAPE Ø Some minerals can be identified by their crystal shapeØ a. CUBIC – Ex. Pyrite, Halite, Galena

OTHER CRYSTAL SHAPES Ø b. HEXAGONAL- six sided crystals Ex. Corundum and Quartz

MORE CRYSTAL SHAPES c. RHOMBIC- shaped like a parallelogram; ex. Calcite

SPECIAL PROPERTIES OF MINERALS Ø Some minerals have very distinctive properties that can be used to identify them: Ø a. Effervescence (acid test) – when HCL (hydrochloric acid) is added to calcium carbonate (Ca. CO 3), it causes bubbling as carbon dioxide (CO 2) is released; ex. ) Calcite is a mineral that bubbles with acid

EFFERVESCENCEAcid test

MORE SPECIAL PROPERTIES Ø b. Double Refraction- an optical property of some varieties of calcite that gives a double image effect.

MORE SPECIAL PROPERTIES Ø c. Magnetism- minerals with this property are attracted to magnets; ex. Magnetite

SPECIAL PROPERTIES CONTINUED Ø d. Fluorescence- property where the mineral glows under ultra-violet light; ex. Fluorite and some calcites

MORE SPECIAL PROPERTIES Ø e. Radioactivity- minerals that contain radium or uranium can be detected by a Geiger counter. They give off radiation (gamma rays).

SPECIFIC GRAVITY Ø Specific Gravity is the heaviness of a mineral as compared to water. It’s similar to density. Pyrite has a s. g. (or density) of 5. 0. Remember water is 1. 0.

MORE ABOUT SPECIFIC GRAVITY Ø Used to compare two similar looking minerals- Pyrite (fools gold) looks like Gold but has a lower specific gravity number

WHAT NOW? Ø It’s time to practice what you have learned about properties of minerals by identifying 15 important minerals. Good luck! Ø Don’t depend on your partner- there will be a challenging mineral lab test at the end of the unit.