Identifying Minerals
- 1. What is a mineral? Found in nature Inorganic: not made from living things Always in a solid form Has a crystal structure Definite Chemical composition: always has the same elements is the same amount
- 2. Identifying Minerals Chapter 2 Section 1 p. 49-54
- 3. Minerals Each mineral has its own specific properties that can be used to identify it. Learning these properties will make it easy to identify minerals.
- 4. Hardness One of the best clues to use is hardness. Mohs hardness scale – invented by Friedrich Mohs in 1812 Ranks 10 minerals from softest to hardest
- 5. Mohs hardness scale 1 - Talc – softest known mineral. It flakes easily when scratched by fingernail. 2 – Gypsum – a fingernail can easily scratch it. 3 – Calcite – A fingernail cannot scratch it, but a copper penny can.
- 6. Mohs continued 4 – Fluorite – A steel knife can easily scratch it. 5 – Apatite – A steel knife can scratch it. 6 – Feldspar – Cannot be scratched by a steel knife, but it can scratch window glass. 7 – Quartz – Can scratch steel and hard glass easily.
- 7. Mohs continued 8 – Topaz – Can scratch quartz. 9 – Corundum – Can scratch topaz. 10 – Diamond – Hardest known mineral. Diamond can scratch all other substances.
- 8. Color Color is easy to identify Color can be used only to identify a few minerals that always have their own characteristic color. Azurite – always blue Malachite – always green
- 9. Streak The streak of a mineral is the color of its powder. You rub the mineral against a streak plate to see the powder. Pyrite – gold in color – black streak Gold – gold in color – golden yellow streak
- 10. Luster Luster is how the mineral reflects light Minerals with metals in them are often shiny. Quartz is glassy. Other terms to describe Luster are earthy, waxy, and pearly.
- 11. Density Each mineral has a characteristic density Density = Mass per unit volume No matter what size of the sample, the density will always be the same. To find the density, measure the mass with a balance and then put the sample in water to find the volume. Use the formula to calculate.
- 12. Cleavage A mineral that splits apart easily along flat surfaces has the property of cleavage . How the atoms in the crystal are arranged will determine if the mineral has cleavage.
- 13. Fracture Most minerals do not split apart evenly. Fracture describes how a mineral will look when it breaks apart in an irregular way. Quartz – shell-like shaped fracture, looks like chipped glass Pure metals – have hackly fracture – form jagged points Some soft minerals that crumble easily have a earthy fracture. Minerals that form rough, irregular surfaces when they are broken have an uneven fracture.
- 14. Special properties Fluorescence – minerals that glow under ultraviolet light Magnetism occurs in a few minerals. A Few minerals are radioactive. Some minerals will react chemically with acid. Some with conduct a small electric current.
- 15. Essential Questions Please answer in complete sentences What properties can you use to determine the type of mineral? Describe how you can test a mineral to determine its hardness, density, and streak. How are cleavage and fracture similar? How are they different? Explain why you can’t rely on any single test or property when you are trying to identify a mineral.