MINERALS: The Building Blocks of Rocks!

1. MINERALS: The Building Blocks of Rocks! S6E5.b Investigate the composition of rocks in terms of minerals.

2. WHAT IS A MINERAL? • A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

3. Let’s Break it Down!!! • Naturally formed = made in nature/not “man-made”. • Inorganic = non-living • Solid = 3 dimensional, hard • Definite crystalline structure = made of two or more elements; forms crystals.

4. Crystals • Solid • Geometric (cubes, hexagons, etc.) • Repeating pattern of atoms or molecules

5. How Many Minerals Have Geologists Discovered? • Geologists have discovered over 2,500. • However, we only see about 100 frequently. • Less than 20 are widely distributed.

6. 2 types of minerals Nonsilicate -does not contain compounds of silicon and oxygen -copper, calcite, galena Silicate -contain a combo of silicon, oxygen and one or more metals -make up 90% of earth’s crust -quartz, mica

7. IDENTIFYING MINERALS • Color • Luster • Streak • Cleavage & Fracture • Hardness • Density • Special Properties

8. COLOR • What you see on the outside! • Not the best way to identify a mineral • Same mineral can come in a variety of colors • Ex: Quartz---purest state is clear; impurities can cause it to be different colors • Exposure to air & water can change color (Ex: pyrite---usually golden but changes to brown or black when exposed to air & water)

9. LUSTER • Luster: the way a surface reflects light; whether a mineral is shiny or dull! • Metallic, submetallic or nonmetallic luster • Shiny = metallic luster • Reflective/dull = submetallic • Dull= nonmetallic luster

11. STREAK • Streak: color of a mineral in powdered form • Rub mineral against a piece of unglazed porcelain (streak plate) • Mark left on streak plate is the streak. • Color of streak not always the color of the mineral sample. • Not affected by air or water • More reliable than color in identifying a mineral

13. CLEAVAGE & FRACTURE • How a mineral breaks • Determined by arrangement of atoms • Cleavage: tendency to break along smooth, flat surfaces (Ex: halite & mica) • Fracture: tendency to break unevenly along curved or irregular surfaces (Ex: quartz)

15. HARDNESS • Mineral’s resistance to being scratched • Mohs Hardness Scale • Ranges from 1 to 10; 1 being softest (talc) & 10 being the hardest (diamond) • Scratch tests; scientists use common items to test hardness. • Fingernail has a hardness of 2-2.5 • Knife blade is 3-4 • Glass is 5-6 • Steel file or nail is 6.5-7

16. A mineral of a given hardness will scratch any mineral that is softer than it is.

17. DENSITY • The measure of how much matter is in a given amount of space. • Density is a ratio of an object’s mass compared to it’s volume. • D=m/v • Measured in grams per cubic centimeter (g/cm3)

18. DENSITY • Water has a density of 1g/cm3 • Used as a reference point for other substances. • Object sinks---it’s density is greater than 1g/cm3 • Object floats---it’s density is less than 1g/cm3

19. SPECIAL PROPERTIES • Only a few minerals have these! • Fluorescence • Chemical reaction • Optical properties • Magnetism • Taste • Radioactivity

21. Most Common Rock-Forming Minerals • Quartz (SiO2) • Calcite (CaCO3) • Augite (Ca, Na) • Hematite (Fe2O3) • Micas • Feldspars

22. Where do we get minerals? • Open pits-quarries (above ground) • Mine shafts (below earth)

23. Reclamation • The process when land is returned to its original state or better • Reduces harmful effects of mining

24. Uses of minerals: • Copper—electrical wire • Gold—jewelry • Galena--batteries

25. Gemstones • Nonmetallic mineral • Valued for their beauty and rarity • Diamonds, ruby, sapphire, emerald, aquamarine, topaz