Mineral Identification Basics: Physical Properties & Characteristics

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

2. COLOR • Some minerals come in more than one color. Ex. Quartz

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

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

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

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

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

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

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

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

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

12. 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

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

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

15. HARDNESS • Hardness- a mineral’s resistance to being scratched • Friedrich Mohs invented Mohs Scale ofHardness • Diamond- hardest mineral; Talc softest mineral

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

17. MNEMONIC DEVICE • To learn Mohs Scale of Hardness, memorize the following sentence: • “To Get Candy From Aunt Fanny, Quit Teasing Cousin Danny.” • 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)

18. MOHS SCALE OF HARDNESS • Talc (softest) To • Gypsum Get • Calcite Candy • Fluorite From • Apatite Aunt • Feldspar Fanny • Quartz Quit • Topaz Teasing • Corundum Cousin • Diamond (Hardest) Danny

19. COMMON OBJECTS TO HELP TEST MINERAL HARDNESS • The following objects can be used to help determine the hardness of a mineral: • Fingernail –Hardness of 2.5 • Copper Penny- H: 3.1 • Iron Nail – H: 4.5 • Glass Plate – H: 5.5 • Steel File – H: 6.5 • Streak Plate – H: 7.0

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

21. CLEAVAGE • Cleavage- the way a mineral may split easily along flat surfaces

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

23. Geologists use hammers and knives to determine how a mineral breaks

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

25. Cleavage can be observed under a microscope in a thin section

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

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

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

29. CRYSTAL SHAPE • Some minerals can be identified by their crystal shape- • a. CUBIC – Ex. Pyrite, Halite, Galena

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

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

32. SPECIAL PROPERTIES OF MINERALS • Some minerals have very distinctive properties that can be used to identify them: • a. Effervescence (acid test) – when HCL (hydrochloric acid) is added to calcium carbonate (CaCO3), it causes bubbling as carbon dioxide (CO2) is released; ex.) Calcite is a mineral that bubbles with acid

33. EFFERVESCENCE-Acid test

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

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

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

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

38. SPECIFIC GRAVITY • 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.

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

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