1. 5.2 Composition and Structure of Minerals Objectives: 1)Identify the characteristics of minerals, 2)Explain how minerals form. 3)List the physical characteristics of minerals that are influenced by their crystalline structure.

2. What is a Mineral? Mineral: has 5 characteristics Occurs naturally Solid Definite chemical composition Atoms are arranged in an orderly pattern Inorganic (never alive)

3. What is a Mineral? Cont’d 8 elements make up 98.5% of the Earth’s crust Most common minerals Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium

4. What is a Mineral? Cont’d More than 90% of the minerals in Earth’s crust are compounds containing oxygen and silicon Most minerals are compounds Native elements: minerals made of single elements Silver, copper, sulfur, diamond Rocks: mixtures of minerals

5. How Minerals Form 4 ways to create minerals Magma Heat Pressure Chemical action Creating crystals lab

6. Structure of Minerals Crystal: a regular geometric solid with smooth surfaces called crystal faces

7. Crystal Structure The arrangement of ions, molecules, or atoms in any mineral determines the shape of the crystal Each type of mineral has its own crystal form

8. Crystal Structure Cont’d The angle at which crystal faces meet is a characteristic for each type of mineral Used to help identify the mineral

9. Crystal Structure Cont’d If space is limited when a mineral is forming, there may not be enough room for crystal faces to develop fully, or “grow” The mineral fills the available space Still crystalline, but faces are not visible

10. Crystal Structure Cont’d Crystals have 6 basic types of shapes Crystallographic axes: Imaginary lines used to distinguish the 7 systems of crystal shapes Each axis passes through the center of the crystal

11. Silicates Silicates: minerals that are compounds including silicon and oxygen May also contain 1 or more metallic elements Few do not contain metal >90% of the minerals in Earth’s crust

12. Silicates Cont’d Silica tetrahedron: the basic building block of a silicate 4 oxygen atoms packed closely around a silicon atom Named for its shape

13. Crystal Structure and Physical Properties Minerals are solid b/c of crystalline structures Atoms, ion, and molecules are closely packed by strong chemical bonds

14. Crystal Structure and Physical Properties Cont’d High temperatures breaks the bonds and causes minerals to melt then to vaporize The temperatures at which a mineral melts and vaporizes are characteristic of the mineral Can sometimes identify a mineral

15. Crystal Structure and Physical Properties Cont’d Cleavage: tendency to split along definite planes Splits along weak bonds between atoms, ions, or molecules of the mineral

16. Crystal Structure and Physical Properties Cont’d Hardness of a mineral depends on the arrangement of its ions, atoms, or molecules and on the strength of the chemical bonds between them

17. Crystal Structure and Physical Properties Cont’d Density depends on the masses of the atoms in the mineral but also on how they are arranged

18. 5.2 Exit Ticket Answer the following questions. Use complete sentences. You may NOT use your book. You MAY use your notes. This is a quiz grade. 1)Identify the characteristics of minerals, 2)Explain how minerals form. 3)List the physical characteristics of minerals that are influenced by their crystalline structure.