5.2 Composition and Structure of MineralsObjectives: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.

What is a Mineral?• Mineral: has 5

characteristics• Occurs naturally• Solid• Definite chemical

composition• Atoms are arranged in

an orderly pattern• Inorganic (never alive)

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

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

How Minerals Form• 4 ways to create

minerals• Magma • Heat• Pressure• Chemical action

• Creating crystals lab

Structure of Minerals

• Crystal: a regular geometric solid with smooth surfaces called crystal faces

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

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

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

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

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

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

Crystal Structure and Physical Properties• Minerals are solid b/c

of crystalline structures

• Atoms, ion, and molecules are closely packed by strong chemical bonds

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

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

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

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

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.