Minerals: Building blocks of rocks

1. Minerals: Building blocks of rocks

2. Introduction What are minerals and how are they different from rocks? What are some of the physical and chemical properties of minerals? What is the most abundant mineral group? What do all minerals in this group have in common? What are some important nonsilicate minerals? When is the term ore used with reference to a mineral? Minerals: Building blocks of rocks

3. Introduction Definitions Minerals versus rocks • rock – an aggregate of minerals • aggregate – minerals occur together as a mixture • each mineral retains its distinctive properties • mineral – a naturally occurring inorganic solid that possesses a definite chemical structure, which gives it a unique set of physical properties Minerals: Building blocks of rocks

4. Introduction Definitions Minerals exhibit the following characteristics: • naturally occuring • inorganic • solid • definite chemical structure Minerals: Building blocks of rocks

5. Introduction Properties of minerals Major properties of minerals: • crystal form • luster • color • streak • hardness • cleavage • fracture • specific gravity Minerals: Building blocks of rocks

6. Introduction Properties of minerals Crystal form – external arrangement of the orderly internal arrangement of atoms Minerals: Building blocks of rocks

7. Introduction Properties of minerals Crystal form – clearly evident only when the mineral forms without space restrictions Crystallization occurs when the KE of individual molecules decreases. Crystals form as they overcome solvation forces Most minerals form under intense competition for space A supersaturated solution readily forms crystals Minerals: Building blocks of rocks

8. Introduction Properties of minerals Luster – appearance or quality of light reflected from the surface Minerals: Building blocks of rocks

9. Introduction Properties of minerals Luster • metallic luster • submetallic luster • nonmetallic luster • vitreous • pearly • silky • resinous • earthy Minerals: Building blocks of rocks

10. Introduction Properties of minerals Color – very unreliable diagnostic property due to impurities Minerals: Building blocks of rocks

11. Introduction Properties of minerals Streak • color of a mineral in its powdered form • use a streak plate • more reliable than color • metallic (dense, dark streak) vs. nonmetallic Minerals: Building blocks of rocks

12. Introduction Properties of minerals Minerals: Building blocks of rocks

13. Introduction Properties of minerals Hardness • resistance of a mineral to abrasion or scratching • use the Mohs scale Minerals: Building blocks of rocks

15. Introduction Properties of minerals Cleavage • a mineral will break along weak bonds when stressed • tendency of a mineral to break along planes of weak bonding • cleavage is described by the number of planes formed and the angles in which these planes meet • not all minerals have definite planes of cleavage Minerals: Building blocks of rocks

16. Introduction Properties of minerals Some examples of cleavage Minerals: Building blocks of rocks

17. Introduction Properties of minerals Fracture • minerals that do not exhibit cleavage tend to fracture when broken • conchoidal fracture – produces smooth curved surfaces • other types of fracture (splinters or fibers) • most minerals fracture irregularly Minerals: Building blocks of rocks

18. Introduction Properties of minerals Some examples of fracture Fibrous fracture – note formation of parallel fibers Conchoidal fracture – note smooth curved surfaces Minerals: Building blocks of rocks

19. Introduction Properties of minerals Specific gravity - compares the weight of a mineral to the weight of an equivalent volume of water Minerals: Building blocks of rocks

20. Introduction Mineral groups Mineral groups Silicates • most common • made of oxygen and silicon • silicon-oxygen tetrahedron is the fundamental building block Minerals: Building blocks of rocks

21. Introduction Mineral groups Variants of the silicate structure • addition of metals to stabilize structure (Fe, Mg, K, Na, Al, and Ca) • sharing of oxygen atoms results to a variety of configurations • single chains • double chains • sheets Minerals: Building blocks of rocks

22. Introduction Mineral groups Minerals: Building blocks of rocks

23. Introduction Mineral groups Variants of the silicate structure • the ratio of oxygen to silicon atoms varies among the different silicate structures • high or low silicon content based on this ratio • important in the formation of igneous rocks • families of minerals • same structure but with varying amounts of metals • olivine, (Mg,Fe)2SiO4 Minerals: Building blocks of rocks

24. Introduction Mineral groups Dark silicate minerals • ferromagnesian silicates • contains iron and/or magnesium • dark color and greater specific gravity Minerals: Building blocks of rocks

25. Introduction Mineral groups olivine hornblende biotite Minerals: Building blocks of rocks

26. Introduction Mineral groups Light silicate minerals • nonferromagnesian silicates • contains Al, K, Ca, and/or Na • light color and smaller specific gravity Minerals: Building blocks of rocks

27. Introduction Mineral groups Light silicate minerals • feldspars – most common light silicates (most common mineral on Earth) • orthoclase feldspar – has K ions • plagioclase feldspar – has Na and Ca • light color and smaller specific gravity • quartz – consists entirely of silicon and oxygen Minerals: Building blocks of rocks

28. Introduction Mineral groups Nonsilicate minerals • carbonate minerals (limestone) • halite (table salt) • gypsum (used in plaster, building materials) • metal ores (Fe, Zn, Pb) • native elements – free occurring, not in compounds (Au, Ag, C) Minerals: Building blocks of rocks