Minerals

1. Minerals 5.2 Composition and Structure of Minerals

2. What is a mineral? • A mineral has the following characteristics: • It occurs naturally. • It is a solid. • It has a definite chemical composition. • Its atoms are arranged in an orderly pattern. • It is inorganic (never alive or produced by something that was alive.)

3. Minerals • There are about 4000 known minerals • Examples) gold, quartz, halite (salt), diamond • 8 elements make up 98.5% of the crust’s total mass. • Most minerals are compounds.

4. Minerals Through the Magma Process • Many minerals form out of molten rock. • In magma, atoms or ions can move freely. • As magma cools the atoms, molecules and ions move closer together and form chemical bonds that create compounds. • Many different minerals can form from the same magma mass. • The types of minerals that form depend on: • The types of elements present in the magma • The rate at which the magma cools determines the crystal size.

5. Minerals Through the Pressure Process • When a rock is subjected to high temperature and pressure, the minerals begin to break down chemically. • The temperature and pressure becomes great enough to change the mineral in a solid state. • The free atoms, ions, and molecules recombine forming new minerals.

6. Structure of Minerals • Minerals form crystals. • A regular geometric solid with smooth surfaces called crystal faces. • Contain a regularly, orderly arrangement of atoms. • Although there are thousands of different minerals, there are only 6 basic different shapes of crystals.

7. Six Crystal Systems

8. Silicates • Silicon and oxygen are the two most abundant elements in the Earth’s crust. • Most minerals (90%) contain these two elements and are called silicates. • A silicate may contain one or more metallic elements. • The basic building block of a silicate is the silicate tetrahedron. • Consists of 4 oxygen atoms around a silica atom. • Named for its shape.

9. Silica Tetrahedron