1. Ch. 4/5 Notes Day 2

2. Objectives
Students will be able to use their senses to identify objects and provide detailed descriptions of them
Students will be able to apply their senses to mineral classification processes to classify common rock forming minerals.

3. The word mineral is used in a variety of ways.
any valuable material extracted from the Earth like coal, gravel, and even groundwater.
by nutritionists for elements metabolized by the body
as anything that isn’t animal or plant
Over 4,000 minerals have been identified in the scientific literature - Approximately new ones are discovered every year!
Luckily, there are relatively few (10-15) common rock-forming minerals.

4. Our Senses 1. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1. 2. 3. 4. 5. 6. 7. 8. 9.
10.

5. Observation Vs. Inference
An observation is something that you "look" and "record" as a statement. (aka FACTS) 
It can be as simple as "It is bright outside."
"The swans in the lake are white."
"The song <insert name of the song you like> is nice.“
Inference is a procedure of logical reasoning, that uses such observations to make/derive other statements. (aka a STORY)
An example of inference is:
Observation 1: The 1st swan is white. Observation 2 : The 2nd swan is white. Observation 3 : The 3rd swan is white Inference: All swans are white.

6. Color Crystal Formation Luster Magnetism Hardness Reaction to HCl acid
Diagnostic Properties of Minerals
Minerals may be identified by different physical and chemical properties. It is important to understand that a minerals is usually identified by a variety of properties. No single property is diagnostic for all minerals.
Common diagnostic properties include:
Color
Crystal Formation
Luster
Magnetism
Hardness
Reaction to HCl acid
Cleavage/Fracture
Density
Streak Color
Smell and/or Taste

7. Color
Color seems like an easy property but it is risky to identify a mineral by its color alone.
Most minerals can have a wide range of colors due to small amounts of impurities in them such as these examples of quartz.
Smokey Quartz
Amethyst Quartz
Citrine Quartz
Rose Quartz
Another example, rubies and sapphires are the same mineral, corundum, and have a wide range of colors! So color alone is not very diagnostic.
Corundum

8. Luster
Luster describes the way that the surface of the mineral reflects light. There are many types of lusters but the common ones are:
Metallic
Nonmetallic
glassy
brilliant
dull

9. Hardness Hardness is a mineral’s ability to resist being scratched.
The Mohs hardness scale is a unitless 10-point scale with each hardness value represented by a common mineral. The Mohs’ hardness scale is not linear!
Hardness can be directly related to bond strength – hardness is an expression of the weakest bond. Compare the hardness of graphite (H=1) and diamond (H=10); they have the same chemical composition but different bonds/structures.

10. Cleavage
Cleavage is the tendency of minerals to break parallel to crystallographic planes along which chemical bonds are weaker than others.
Cleavage surfaces are not necessarily parallel to crystal faces.
It may be difficult to distinguish between cleavage planes and crystal faces.

11. Fracture
Fracture is the way a mineral breaks in the absence of a cleavage plane. In some crystals, the strength of bonds is approximately equal in all crystallographic directions. Several types of fracture can be described:
conchoidal – smooth curved surfaces resembling shells
fibrous – common with asbestos
hackly – jagged fractures with sharp edges
irregular or uneven – rough or irregular surfaces
Conchoidal fracture in obsidian.
Fibrous fracture in chrysotile.
Hackly fracture in native copper.

12. Streak
A mineral’s streak is the color of a powdered mineral on a streak plate (unglazed porcelain tile).
This property can be diagnostic for a small number of minerals (usually those with a metallic luster).
Although the color of a mineral may vary, the color of the streak remains surprisingly constant.

13. Magnetism Reaction to Acid
Magnetism in minerals results from atomic properties of certain metal atoms in minerals.
This property is diagnostic for a few minerals such as magnetite.
Reaction to Acid
Minerals that contain the chemical component carbonate (CO32-) react to acid by effervescing.
The mineral calcite effervesces by the reaction:
CaCO3 + 2HCl —>
CO2 + Ca2+ + 2Cl- + H2O

14. Other Properties
There are many other physical properties that may be diagnostic for some minerals.
Play of color
Smell/Taste
Luminescence
It is important to understand that not all properties are diagnostic for all minerals.
asterism

15. Ch. 4/5 Notes Day 3

16. Objectives

17. Silicate vs. Non-Silicate classification of minerals
ALL MINERALS ON EARTH FALL INTO ONE OF THESE CLASSIFICATIONS

18. Two main Divisions of Minerals (Silicate and Non-silicate)
Silicates (95 % of Earth’s Crust)
Non-Silicates (5% of Earth’s Crust)
Contain silicon (Si) and oxygen (O)
Silicate Types:
Quartz (SiO2)
Feldspar
Orthoclase Feldspar (KAlSi3O8)
Plagioclase Feldspar (NaAlSi3O8  CaAl2Si2O8)
Ferromagnesian Minerals
Hornblende (Ca2Fe5Si8O22F2)
Olivine Fe2SiO4
Muscovite (KAl2(AlSi3O10)F2)
Biotite (KMg3AlSi3O10(OH)2)
DO NOT CONTAIN SILICON!!!
Carbonates – contain carbonate (CO3)
Calcite (CaCO3)
Dolomite (CaMg(CO3)2)
Sulfates – contain sulfate (SO4)
Gypsum (CaSO4)
Halides – contain (Cl, F with Na, K, Ca)
Halite (NaCl)
Fluorite (CaF2)
Oxides – contain oxygen (O) and NOT silicon (Si)
Hematite (Fe2O3)
Magnetite (Fe3O4)
Native Elements – uncombined with other elements
Silver (Ag)
Copper (Cu)
Sulfides – contain sulfur (S)
Galena (PbS)
Pyrite (FeS2)

19. Silica content And mineral properties
Silica-Rich Minerals
Silica-Poor minerals
Melt at lower temperatures
Last to crystallize from cooling magma
More resistance to chemical weathering
Melt at higher temperatures
Tend to crystallize earlier in cooling magma
Less resistance to chemical weathering
silica-rich feldspar
silica-poor olivine

20. Using Crystal structure to Identify Minerals

21. Crystalline Structure
Minerals have an organized distribution of atoms.
Crystals are an outward display of internal atomic geometry.
Bond strength affects the minerals resistance to breakdown.
Basic building block of silicates is the SiO4 tetrahedron.

22. Types of silicate CRYSTALS AND chains
ALL SILICATES ARE BUILT WITH THE SiO4 TETRAHEDRON.
Tetrahedron Variations
Independent tetrahedron family- Olivine
Single-chain tetrahedral family (Share 2 oxygen) Ex. Pyroxenes.
Double-chain tetrahedral family (2-3 oxygen shared) Ex. Hornblende
Sheet tetrahedral family (3 shared Oxygen) Ex. Micas
Network family (all 4 Oxygen shared) very strong bonds Ex. Quartz

23. Crystal Structures of Non-Silicate Minerals

25. Crystal Form
Some minerals that grow without being impeded by their environment develop characteristic crystal shapes or crystal form that represents the symmetry of the crystal structure. Crystal form can be a diagnostic property for some minerals.
Quartz has an internal structure that has a 6-sided (hexagonal) symmetry. As a result, quartz crystals commonly are 6-sided.
Halite has an internal structure that has a cubic (4-sided) symmetry. As a result, halite crystals commonly are cube shaped.