1. Minerals

2. Why should we care? Nearly all manufactured
products we use are obtained
from minerals.
aluminum: soft drink cans
graphite (carbon): our pencil lead
copper: wire for our electricity
talc: baby powder
silver & gold: our jewelry
silicon: our computer chips

3. Important geologic events that
affect us involves rocks and minerals.
volcanic eruptions
earthquakes
weathering and erosion
mountain building

4. We know what a MINERAL is, but what is a ROCK?
1) is solid;
2) contains a mixture of one or more minerals; and
3) occurs naturally as part of our planet.

5. rock
minerals
mineral

6. Example From Textbook:
Figure 2.2
Granite & constituent minerals

7. rock mineral minerals collection of one or more A collection
So far we have:
rock
collection of
one or more
minerals
mineral
A collection
of one or more
types of atoms

8. Mineral Properties
Each and every mineral has certain mineral properties. The properties of each mineral depends on the following:
1) The type of elements present (i.e. composition)
2) The arrangement of atoms (i.e. structure)
3) The strength of bonding (i.e. ionic, covalent (molecular), or metallic)
Reference: Tarbuck and Lutgens Pages

9. Reminder - Bonding How do different atoms combine? Bonding
3 Main Ways:
“ionic bond” – lose or gain electrons to form ions. Positive ions (cations) attract negative ions (anions).
“covalent bond” - sharing electrons.
“metallic bond” - electrons are free to move about from atom to atom.

10. Halite
Halite (Rock Salt) is brittle in nature due to the ionic bonding between the sodium and chloride ions.

11. Speaking of Atomic Arrangement (Structure)
Consider diamond versus graphite!
Note that completely different minerals can form from the same atom, depending on how the atoms are arranged.
↑ pressure = closer packing of atoms = different substance.
Temperature and pressure conditions under which minerals form are very important.

12. Diamond Versus Graphite
Diamond and graphite are polymorphs of the element carbon; however, they differ in terms of the mineral properties hardness and cleavage due to arrangement of the carbon atoms.
Diamond is hard and has no cleavage since the carbon atoms are arranged in a network covalent structure. This does not allow for any weak planes of bonding.
Graphite is soft and has perfect basal cleavage (sheets) since the carbon atoms are arranged in planes of strong bonding with planes of weak bonding in between.

13. Used as pencil lead lubricant Crystal structure: sheets of pure carbon
Graphite:
Soft gray material
Used as pencil lead lubricant
Crystal structure: sheets of pure carbon
Diamond:
Forms deep in Earth at high pressures
Pure Carbon
Hardest substance known to humans
Crystal structure: dense and compact

14. Quartz Versus Mica
Quartz and mica could also be compared and contrasted. They compare in that both are comprised of the silicon-oxygen tetrahedron. They contrast in that quartz exhibits fracture and mica exhibits basal cleavage. I.E. Structure and Bonding

15. Mineral Properties
The following are a list of physical properties that minerals could display:
1) Specific Gravity – LATER so important its own class
2) Hardness
3) Cleavage Versus Fracture
4) Streak
5) Luster
6) Colour
7) Others
Taste, Feel, Magnetism, Acid Test, Crystal Form, Smell, Double Refraction, Tenacity, and Fluorescence.

16. Hardness Definition: The resistance of a mineral to scratching.
Hardness is expressed in terms of Moh’s Hardness Scale, which ranks relative hardness from 1 – 10.
You could use a rhyme to remember the hardness scale:
Tonight Ghosts Come From Africa
On Quads To Catch Dinosaurs

18. Hardness
The following objects can be used when trying to determine the hardness of different minerals:
If the object scratches the mineral, then the object is harder than the mineral.

19. Hardness
Mineral scratches a piece of glass (hardness of 5.5). Mineral is harder!
Nail - hardness of 4.5 scratches a mineral. Mineral is softer!
Fingernail - hardness of 2.5 scratches a mineral. Mineral is softer!

20. Cleavage
Definition: The tendency of some minerals to break along smooth, flat, parallel surfaces.
Cleavage follows areas of weak bonding.
Cleavage directions are determined by atomic structure as well as the strength of bonding.
MICA

21. Cleavage Plane Directions
Minerals show cleavage in many different directions, but most common are in planes of one, two, and three directions.
Cleavage in one direction is called basal cleavage. Example: Mica

23. Cleavage Plane Directions
Cleavage in two directions. Example: Orthoclase feldspar displays this type of cleavage.

24. Cleavage Plane Directions
Cleavage in three directions. Examples: Halite, Galena, and Pyrite.

25. Calcite also got three directions of cleavage.

26. Fracture
A mineral that do not have any cleavage planes is said to break by “Fracture“, which is the tendency of a mineral to break irregularly. Example is glass or the mineral quartz, which is said to have Conchoidal Fracture. This is a curved breakage that resembles the concentric shape of a mussel shell.

27. Fracture
Another example of a mineral that fractures is asbestos. This mineral displays a Fibrous Fracture.

28. Streak
The true color of the mineral. It is the colour of the mineral in its powdered form.
To find the streak of a mineral, you must perform a streak test. To do this, you scratch a mineral across an unglazed porcelain tile and the powder streak left on the tile is the true color of the mineral.

29. Luster The appearance of the mineral in reflected light.
Most minerals can be described as either:
1. Metallic OR
2. Non-Metallic
A) Glassy
B) Greasy
C) Earthy or Dull
D) Pearly

30. Metallic Luster Most minerals can be described as: Metallic Pyrite
Galena

31. Non-metallic Glassy Luster
Halite
A) Glassy
Calcite

32. Non-metallic Greasy Luster
B) Greasy

33. Non-metallic Earthy (Dull) Luster
C) Earthy . or Dull

34. Non-metallic Pearly Luster
D) Pearly

35. Colour The actual colour of the mineral that you see.
This property is less distinctive. (not as reliable as the others) WHY?
Three reasons:
1) Different minerals can have the same color.
Halite
Calcite

36. Various blue minerals.

37. Color
2) Some minerals may have impurities, which cause a single mineral to have different colors.
Impurities simply mean a little more of one or more elements.

38. Varieties of the mineral quartz. Transparent or colourless when pure.

39. 3) Surface oxidation can change a minerals color.

40. Sample Problem Answer:
Explain why colour is NOT a reliable property for identifying minerals.
Answer:
A single mineral may have different colours due to the presence of impurities. Examples include various colors of quartz, fluorite, calcite, etc. Also, different minerals can have the same color. Examples include minerals such as halite, gypsum, calcite, etc. Or minerals may have experienced surface oxidation.

41. Other Properties
These properties can be helpful to identify minerals that are similar:
Taste - What the actual mineral tastes like! Example: Halite (rock salt) tastes salty.
Feel - What the mineral feels like! Example: Graphite – greasy
Example: Talc - soapy

42. Other Properties
These properties can be helpful to identify minerals that are similar:
Magnetism - If a mineral is magnetic or not! Example: Magnetite (Loadstone) will attract metal objects.
Acid Test - Drop acid on the sample to see if the mineral reacts (i.e. fizzes). This test is used to test the carbonate group. Example: Calcite (which makes up the rocks limestone and marble).

43. Other Properties
Smell: The mineral sulfur smells like rotten eggs.

44. Other Properties
Double Refraction: This is an optical property. For example, when a transparent piece of calcite is placed over printed material, the letters appear double.

46. Other Properties Tenacity:
Mica (muscovite and biotite) will bend and elastically snap back.
Gold is malleable, which means that it can be hammered into sheets.

47. Other Properties
Crystal Form (Shape): Already completed in the notes.

48. Crystal Form - Remember
Shape or form of a crystal can reflect the orderly internal arrangement of atoms.
Example: Quartz
(SiO2)

50. Crystal Faces
The smooth flat surfaces on crystals are called faces.

51. Other Properties
Fluorescence: When light from a source strikes a mineral and reacts with the component chemicals, thereby making the mineral glow. Example: Gypsum

53. Sample Problem
Explain how the specific gravity of a mineral is determined.
Answer:
Specific gravity compares the weight of a mineral to the weight of an equal volume of H2O.
Find the mass of the mineral; using a scale or balance.
Find the volume of the mineral; using the water displacement method.
Find the weight of the mineral in water; by suspending the mineral from the spring scale and weighing it immersed in water.
Use the formula;
S.G. = density = m/v OR
S.G. = (weight of mineral in air)
(weight in air) - (weight in H2O)

54. Careers Would you like to be a geochemist or a mineralogist?
Geochemistry: The study of the chemical composition of Earth and other planets, chemical processes and reactions that govern the composition of rocks (minerals make up rocks) and soils, and the cycles of matter and energy that transport Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere.
Mineralogy: The study of chemistry, crystal structure, and physical (including optical) properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.

55. Careers
What about a gemologist or a crystallographer?