Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chapter 3: Matter and Minerals (part II)

Similar presentations

Presentation on theme: "Chapter 3: Matter and Minerals (part II)"— Presentation transcript:

1 Chapter 3: Matter and Minerals (part II)

2 Minerals: the building blocks of rocks
Definition of a Mineral: naturally occurring inorganic solid characteristic crystalline structure definite chemical composition

3 How do we identify minerals?
Physical properties: Color Luster Hardness Crystal shape Cleavage Specific gravity Other

4 Physical Properties of Minerals
Color: Most obvious, but often misleading Different colors may result from impurities Example: Quartz

5 Physical Properties of Minerals
Color: Streak – color of a mineral in powdered form (used for metallic minerals) Obtained by scratching a mineral on a piece of unglazed porcelain. Example: Hematite

6 Physical Properties of Minerals
Luster: How a mineral surface reflects light Two major types: Metallic luster Non-metallic luster Metallic example: Galena Non-metallic example: Orthoclase

7 Physical Properties of Minerals
Hardness: How easy it is to scratch a mineral Mohs Scale of Hardness relative scale consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

8 Mohs Scale of Hardness Hardest (10) – Diamond Softest (1) – Talc
Common objects: - Fingernail (2.5) - Copper penny (3.5) - Wire nail (4.5) - Glass (5.5) - Streak plate (6.5)

9 Physical Properties of Minerals
Crystal shape (or form): external expression of a mineral’s internal atomic structure planar surfaces are called crystal faces angles between crystal faces are constant for any particular mineral Quartz Pyrite

10 Physical Properties of Minerals
Cleavage vs. Fracture: The way a mineral breaks Cleavage: tendency of a mineral to break along planes of weakness Minerals that do not exhibit cleavage are said to fracture Do not confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken.

11 Physical Properties of Minerals
Cleavage is described by: Number of planes Angles between adjacent planes These are constant for a particular mineral

12 Physical Properties of Minerals
Cleavage (1 direction): Example: mica

13 Physical Properties of Minerals
Cleavage (2 directions): orthoclase amphibole

14 Physical Properties of Minerals
Cleavage (3 directions): halite calcite

15 Physical Properties of Minerals
Cleavage (4 directions): fluorite

16 Physical Properties of Minerals
Fracture: minerals that do not exhibit cleavage are said to fracture smooth, curved surfaces when minerals break in a glass-like manner: conchoidal fracture Quartz

17 Physical Properties of Minerals
Specific gravity: weight of a mineral divided by weight of an equal volume of water metallic minerals tend to have higher specific gravity than non-metallic minerals Galena SG=7.5 Quartz SG=2.67

18 Physical Properties of Minerals
Other properties: reaction with hydrochloric acid (calcite fizzes) taste (halite tastes salty) feel (talc feels soapy, graphite feels greasy) magnetism (magnetite attracts a magnet)

19 Mineral Groups Rock-forming minerals
~30 common minerals make up most rocks in Earth’s crust Composed mainly of the 8 elements that make up over 98% of the crust

20 SILICATES Mineral Groups Common cations that bond with silica anions
Element Abundances Silica (SiO4)4- SILICATES Common cations that bond with silica anions All others: %

21 Mineral Groups Silicates (most abundant)
Non-silicates (~8% of Earth’s crust): Oxides O2- Carbonates (CO3)2- Sulfides S2- Sulfates (SO4)2- Halides Cl-, F-, Br- Native elements (single elements; e.g., Au)

22 Mineral Groups – Silicates
Tetrahedron fundamental building block 4 oxygen ions surrounding a much smaller silicon ion Silicon-oxygen tetrahedron (SiO4)4-

23 Mineral Groups – Silicates
Joining Silicate Structures How tetrahedra may be linked: independent tetrahedra single chains double chains sheets 3-D framework

24 Mineral Groups – Silicates –

25 Mineral Groups – Silicates
Olivine Group dark silicates (Fe-Mg)  ferromagnesian No cleavage

26 Mineral Groups – Silicates
Pyroxene Group Ferromagnesian / dark silicates (Fe-Mg) Augite 2-directions of cleavage (at nearly 90 degrees)

27 Mineral Groups – Silicates
Amphibole Group Ferromagnesian / dark silicates (Ca, Fe-Mg) Hornblende 2-directions of cleavage (not at 90 degrees)

28 Mineral Groups – Silicates
Mica Group and Clay Minerals light silicates (K, Al)  non-ferromagnesian Muscovite 1-direction of cleavage

29 Mineral Groups – Silicates
Feldspar Group light silicates (K-Na-Ca, Al) K-feldspar Most common mineral group Orthoclase Plagioclase 2-directions of cleavage (at 90 degrees) Ca/Na-feldspar

30 Mineral Groups – Silicates
Quartz light silicates (pure SiO2) no cleavage (conchoidal fracture) hard, resistant to weathering Quartz

31 Mineral Groups Non-ferromagnesian Silicates (K, Na, Ca, Al)
Silicates (Fe, Mg) Oxides Carbonates Sulfides/sulfates Native elements

Download ppt "Chapter 3: Matter and Minerals (part II)"

Similar presentations

Ads by Google