1. Minerals
2/11/14

2. Rocks and Minerals
A rock is a solid combination of minerals or mineral materials
A mineral is a naturally occurring, inorganic solid with a crystal structure and a characteristic chemical composition
Today, we are going to focus on minerals…

3. Minerals
Minerals are inorganic, which means that living things did not produce them
Is coal a mineral?
Is concrete a mineral?
No, coal is created from the remains of plants
No, concrete is human manufactured and made from a variety of natural materials

4. Minerals
Each mineral is a unique substance with its own chemical composition and crystal structure
Within each mineral, the chemical composition is nearly constant
Pyrite is made of iron and sulfur (FeS2)

5. Minerals Minerals are the building blocks of rocks
Over 4,000 minerals exist
Only a fraction are common
Common minerals are call rock forming minerals

6. Properties of Minerals
Crystal Structure
Atoms are arranged in a particular geometric shape
Size of mineral’s crystal structure can vary for the same type of mineral
Examples of structure include:
Cubes, sheets, needles, and threads
Pyrite has a cubic crystal structure 

7. Properties of Minerals
Color
SOME minerals can be identified by a characteristic color
Color can be deceptive due to slight changes in composition

8. Properties of Minerals
Streak
Streak is the color of the mineral’s powder on a streak plate
It is found by scraping the mineral across a piece of unglazed porcelain (streak plate)
The color of the streak is not always the same color as the mineral itself

9. Properties of Minerals
Luster
Luster is the way in which its surface reflects light
Refers to general appearance of a mineral (how shiny it is)
Terms used to describe luster include:
Silky, pearly, vitreous (glassy), earthy, metallic, greasy
Pearly
Earthy
Vitreous

10. Properties of Minerals
Density
Density depends on chemical composition
Density describes how “Tightly Packed” the atoms and molecules are. (Density = mass/volume)
The densest elements are the METALS in the Middle of the Periodic Table
The least dense elements are at the ENDS of the periodic table (group 1 and 8)
Galena is made mostly of lead
so its density is about 7.5 g/cm3

11. LESS. Oxygen is naturally a gas, and silicon is a metalloid
LESS! Oxygen is naturally a gas, and silicon is a metalloid. Lead is a dense element in the middle of the transition METALS.
Does Quartz, which is made of Silicon (Si) and Oxygen (O), have a higher or lower density than Galena (Pb)?

12. Properties of Minerals
Hardness
Atoms in different minerals are held together by chemical bonds of different strengths, resulting in a different hardness
Hardness is the resistance to scratching
“Moh’s Hardness Scale”

14. Check for Understanding
Which mineral can scratch Gypsum but cannot scratch Fluorite?
What are three different ways to classify a mineral’s luster?
What is Streak?
Calcite!
Glassy, greasy, metallic
Color of the mineral’s powder

15. Properties of Minerals
Fracture and Cleavage
Fracture of a mineral is how the mineral breaks
Uneven or curved (chonchoidal)
Cleavage is a type of fracture in which the mineral tends to split along regular, well-defined planes where the bonds are the weakest
Blocks, sheets, etc.

16. Properties of Minerals
Other Properties
Acids
Magnetite
Fluorescence
Electrical
Refraction