1. Earth Science Chapter 4 Section 1
What is a Mineral?
Earth Science
Chapter 4
Section 1

2. Mineral Characteristics
Naturally occurring
Inorganic
Solid
Specific chemical composition
Definite crystalline structure

3. Rock Forming Minerals 3000 minerals occur in Earth’s crust
8-10 refered to rock forming minerals
Make up most of the rocks

4. Minerals from Magma Magma less dense than surrounding rocks
Rises
As cools, crystals form
Elements in magma determine the mineral formed
Large crystals
Cool slowly, atoms have time to arrange in large crystals
Small crystals
Rapidly cooling magma

5. Minerals from Solution
Minerals dissolved in water
Salts
Saturated
Water can’t hold any more of the substance
Supersaturated - Precipitates
Solution becomes overfilled
Conditions right for minerals to form
Individual atoms bond together and mineral crystals form into solids from the solution

6. Minerals form Solutions
Evaporates
Minerals crystallize when the solution evaporates

7. Crystal Form Distinct crystal shape Easily recognizable
Halite- cubes
Quartz - double pointed ends
Perfect crystals are not the norm
Crystallization should not be used as only form of identification

8. Luster Metallic luster Nonmetallic luster
Shiny surfaces that reflect a lot of light
Nonmetallic luster
Do not shine
Dull, pearly, waxy, silky or earthy

9. Hardness
Hardness is the measure of how easily a mineral can be scratched.
Most useful and reliable of all tests
Mohs Hardness Scale used to compare minerals

10. Cleavage and Fracture
Cleavage
Fracture
A mineral that splits easily alone one or more flat planes
Minerals that bread with rough jagged edges
Conchoidal fracture

11. Streak
The powder left on a ceramic plate when a mineral is scratched along it.
Does not always match the color of the mineral.

12. Color Most noticeable characteristic Least reliable
Sometimes caused by trace elements or compounds within the mineral

13. Special Properties Magnetism Striations Double refraction
Light is split into two rays
Effervescence
Does if fizz?
Fluorescence
Shine in ultraviolet light

14. Texture How the mineral feels to the touch Subjective
Used with a combination of tests

15. Specific Gravity
Ratio of the weight of the mineral with the weight of an equal volume of water.
Specific gravity of minerals can be roughly relatively tested using heft.