1. Chapter 14 Minerals & Ores

2. Mineral  A naturally occurring, inorganic, crystalline solid with a definite chemical composition  Rock containing one or more minerals (or metals) (or metals)  Sources of elements or compounds important to industry or agriculture Ores

3. Minerals  Almost 4000 minerals found to exist  3 classes of matter: elements, compounds, & mixtures  Elements: made of same kind of atom (same number of protons)  Native mineral: a mineral which is a pure element Ex: gold, silver, aluminum, etc.

4.  Compounds: 2 or more elements combined in a fixed ratio  Ex: quartz  Most minerals are compounds  Pure substance: made of only 1 element or 1 compound

5.  Mixtures: several elements or compounds combined but not in a fixed ratio, proportions can vary because they are not bonded chemically  Ex: salt water – amount of salt in water can vary  Rocks  But minerals are never mixtures!

6. Mineralogists  Geologists who specialize in identifying minerals  Look at a properties, do tests

7. Characteristics of Minerals  1) Color  Many minerals have same color  Some colors due to impurities in mineral  Ex: Quartz  Color can change when exposed to air

8. Characteristics of Minerals  2) Streak  Color of a mineral’s powder on unglazed porcelain  A mineral’s streak does not change due to impurities  Better indicator than color alone

9. Characteristics of Minerals  3) Luster: Quality and intensity of light reflected from its surface  Types:  Metallic  Vitreous (glassy)  Pearly  Adamantine (diamond)  Dull  Greasy  Resinous  Earthy

10. Characteristics of Minerals  4) Crystal Shape  Each mineral has a characteristic crystal shape with fixed angles  Crystals enlarge by adding particles (Accretion)

11. Characteristics of Minerals  5) Cleavage  Characteristic of splitting along certain planes due to weak bonding

12. Characteristics of Minerals  6) Fracture: Characteristic way of breaking but not in cleavage planes  Types:  Conchoidal – smooth curved surfaces (Ex: obsidian, flint)  Fibrous – splinters or fibers (Ex: asbestos)  Uneven – irregular & rough  Hackly – fine, sharp points (Ex: iron, copper)

13. Characteristics of Minerals  7) Hardness  Ability to withstand scratching & abrasion  Hardness test – scratch the mineral with various objects & rate it  The Mohs scale: 1-10  Talc = 1, softest  Diamond = 10, hardest

14. Characteristics of Minerals  8) Specific Gravity  Ratio of the mass of a substance with the mass of an equal volume of water at 4°C  Can sometimes estimate just by lifting (some rocks feel lighter)

15. 14B-2 Characteristics of Minerals (cont.)  9) Flame test  Wire dipped in mineral powder put in flame  Some minerals produce a characteristic color when you burn them

17. Characteristics of Minerals  10) Acid test  Put hydrochloric acid on the mineral and some minerals give off bubbles (fizzes – called effervescence)  Used to identify carbonates, sulfides, & sulfites

18. Characteristics of Minerals  11) Magnetism  Some minerals can attract bits of iron  Ex: magnetite or loadstone  used in 1 st compass

19. Characteristics of Minerals  12) Radioactivity  Can use radiation detector to find radioactive minerals (contain uranium)  Ex: pitchblende

20. Characteristics of Minerals  13) Luminescence  Mineral glows due to absorbing ultraviolet light  Fluorescent: glows while under the light  Ex: Calcite  Phosphorescent: continues to glow when light removed

21. Characteristics of Minerals  14) Refraction  Bending light passing through mineral  Some produce double refraction (double image)

22. BW  Prepare for quiz on 14B