Minerals: Teacher’s Notes

2.1 Minerals are all around us Four characteristics of Minerals: Rocks only have two of the characteristics that a mineral has… solid and forms naturally. Formed in nature Is a solid: definite volume and rigid shape Definite chemical makeup: consists of a specific combo of atoms of certain elements Crystal structure: a crystal is a solid in which the atoms are arranged in an orderly, repeating three-dimensional pattern

Minerals are grouped according to composition… ✘ Silicates: most common group; contain oxygen and silicon- the two most common elements in the Earth’s crust Most common silicates are quartz, feldspar, and mica ✘ Carbonates: 2 nd most common group; contain carbon and oxygen joined together ✘ Other non-rock forming mineral groups include oxides, which form many metals (tin, copper, hematite)

2.2 A mineral is identified by its properties A mineral’s appearance helps identify it: ✘ Color and Streak Streak: color of the powder left behind when the mineral is scraped across a surface  Luster The way in which light reflects from a mineral’s surface

The way a mineral breaks helps identify it:  Cleavage Tendency of a mineral to break along flat surfaces  Fracture Tendency of a mineral to break into irregular pieces

A mineral’s density and hardness help identify it: ✘ Density: the amount of mass in a given volume of the substance ✘ Example: Gold and pyrite (fool’s gold) look alike, but gold is much more dense.

A mineral’s density and hardness help identify it: CONTINUED ✘ Hardness: a mineral’s resistance to being scratched (harder minerals have stronger bonds between atoms) ✘ The Mohs scale describes a mineral’s hardness (A diamond is the hardest of all minerals: 10 on the Mohs scale) *fun fact: a mineral can only be scratched by another mineral that has the same hardness or stronger

Some minerals have special properties: ✘ Some carbonates react with acid ✘ Some have Florescence (glow when exposed to ultraviolet light) ✘ Some respond to magnets ✘ Some have radioactivity: their elements change into other elements over time and release energy

2.3 Minerals are valuable resources Minerals have many uses in industry: 1. Metals for cars/airplanes 2. Quartz and feldspar for glass 3. Fluorite and calcite for toothpaste 4. Silver compounds for photo film 5. Mica and talc for paint

Minerals are valuable resources Minerals have many uses in the arts. 1. Gemstones for jewelry 2. Ground up minerals make pigments for dyes and paints 3. Ceramics, paper, cosmetics are made from minerals

Minerals form in many ways. 1. Water evaporates When water evaporates, minerals are left behind Ex: Halite (Salt) 2. Hot water cools Hot water within Earth’s crust moves through rocks, dissolving minerals in the process. The minerals then separate from the water and become solid again. Ex: Gold 3. Molten rock cools Magma: molten rock inside the Earth…as it cools, atoms join together and form minerals Ex: Quartz Lava: molten rock that has reached Earth’s surface

Minerals form in several ways. CONTINUED 4. Heat and pressure cause changes Atoms break apart and join again Ex: Garnet 5. Organisms produce minerals Human body produces apatite in bones and teeth Oysters/clams produce Calcite

Many minerals are mined. ✘ Ores: rocks that contain enough of a mineral to be mined  Surface Mining: minerals are recovered at or near Earth’s surface a) panning b) strip mining c) open pit mining  Deep Mining: minerals recovered far below Earth’s surface Ex: Naica cave