1. Eric Christiansen

2. Minerals Substance of the Earth Letters Elements Words Minerals
Sentence Rocks
Paragraph Outcrop, mountain, volcano

3. 02_01.JPG Figure 02-01 Title: What you see in a rock. Caption:
Many rocks look uniform from a distance, but on closer examination consist of smaller components, called minerals.

4. The Nature of Minerals Mineral
A naturally occurring inorganic solid that has a fixed chemical composition with an orderly internal arrangement of atoms.

5. Elements Minerals are made of elements Elements are made of Atoms
The smallest unit of an element that retain its properties
Small nucleus of protons and neutrons
Surrounded by a “large” cloud of electrons

6. The Nucleus Protons Positive electrical charge
Mass equal to 1 atomic unit
1 atomic unit = 1.66 * 10-24g
The number of protons in the nucleus determines the atomic number

7. The Nucleus
Neutrons
Electrically neutral
Mass of 1 atomic unit
The number of neutrons plus protons equals the atomic mass
The number of neutrons in the nucleus of may vary producing isotopes but the number of protons does not change in a single element

8. Electrons Electrons form clouds around nucleus
Negative electrical charge
Mass is much less than 1
Not a significant contribution to the mass of the atom
Number of Electrons = Protons in electrically neutral atom
Loss or gain of electrons produce ions

9. Ions Atoms may gain or lose electrons Noble gas electron structure
Loss of electrons makes a positively charged ion +cation
Gaining electrons makes a negatively charged ion -anion
Oppositely charged ions may attract one another to make a chemical bond

10. Periodic Table of the Elements
Each of the 92 elements has a different number of protons in its nucleus. There are only about 10 elements that are abundant and therefore common in minerals.
Fig. 3.3

11. Periodic chart: Element Properties
Atomic number
Protons
Charge
Lost (or gained electrons)
Ionic radius

13. Bonding Atoms are stable when their outermost electron shell is filled
Electron structure like a noble gas
Atoms lose, gain or share electrons to achieve a noble gas structure
Types or bonds
Ionic Covalent Metallic

14. Bonding Ionic bonds Covalent bonds Metallic bonds
Formed between ions of opposite charge
Covalent bonds
Atoms share electrons to achieve noble gas structure
Very strong compared to most ionic bonds
Metallic bonds
Outer electrons are mobile
Electrical conductivity high

15. Ionic Bonding
Fig 3.4A

16. Covalent Bonding
Fig 3.4B

17. States of Matter
Solid
Crystalline - atoms bond together in a regular orderly pattern
Amorphous – atoms in a random pattern
Liquid - atoms or molecules tightly packed but in random motion
Gas - particles in random motion at high speeds, separated by empty space

18. The Nature of Minerals Mineral
A naturally occurring inorganic solid that has a fixed chemical composition with an orderly internal arrangement of atoms.
I don’t like to emphasize the naturally occuring inorganic part of the definition. It is old fashioned and neglects important solids.

19. Minerals Must be solid A fixed chemical composition
Ice vs. liquid water
A fixed chemical composition
Ice vs. seawater
An orderly internal arrangement of atoms
Quartz versus glass (or obsidian)
Must be formed by a natural process?
Synthetic diamonds and other gemstones would not be minerals
Must be an inorganic compound?
Coal is not a mineral by this standard.

20. Minerals Internal structure Repetitive geometric pattern of atoms
Expressed in physical properties
Crystal shape
Cleavage

21. Polymorphism Same elemental composition but different structure
Different physical properties
Fig 3.17

22. Common Polymorphs: Calcite and Aragonite
Calcite=CaCO3
Aragonite=CaCO3

23. Minerals Definite composition
Chemical composition expressed as a chemical formula
Composition ranges from simple to complex
Native copper - Cu
Biotite - K(Mg,Fe)3AlSi3O10(OH)2
Ionic substitution may occur causing small variations in composition

24. Physical Properties of Minerals 1. Crystal Form 2. Density 3. Cleavage
4. Fracture
5. Hardness
6. Color
7. Streak
8. Luster
Discussed more in lab

25. Physical Properties Density Ratio of mass to volume
Common rock-forming minerals range from 2.6 to 3.4 grams/cm3
Pyrite g/cm3
K feldspar 2.6 g/cm3

26. Quartz crystals—faces are not cleavage surfaces
Physical Properties
Crystal faces & form
Growth in unrestricted environment
Form reflects symmetry of internal structure
Quartz crystals—faces are not cleavage surfaces

27. National Geographic

28. Physical Properties Cleavage
Breakage along parallel planes of weakness
Related to internal structure -weaker bonds
May occur in 1 or more planes
Fracture is uneven breakage - no natural planes of weakness

29. Cleavage Planes
Fig. 3.9 A & D

31. Mineral Stability Stability ranges
Range of pressure, temperature and composition under which a mineral forms
Stable
Exists in equilibrium with its environment
Metastable
A mineral existing outside its stability range

32. Stability Ranges for SiO2
Fig 3.11

33. Silicate Minerals Most common minerals on Earth
Comprise 95% of the volume of the crust
Approximately 75% of the Earth’s mass is made up of silicon and oxygen
All silicate minerals are based on the silica tetrahedron
SiO4-4

34. Silicon-Oxygen Tetrahedron
All silicate minerals are based on the silica tetrahedron
SiO4-4
Fig 3.18

35. Silicate Minerals
Silica tetrahedron may polymerize to form a variety of geometric structures, alone or in combination with other cations
Isolated tetrahedra
Single chains of tetrahedrons
Double chains
2-D sheets
3-D frameworks

36. Silicate Minerals Amphibole (Hornblende) Olivine Pyroxene
Clay’s & Mica
Quartz
Feldspars
Fig 3.19

37. Silicate Structures Chain Double chain Isolated Sheet Framework
Fig 3.19

39. Minerals Internal structure Repetitive geometric pattern of atoms
Expressed in physical properties
Fig 3.17

41. Rock-Forming Minerals
About 20 common minerals make up most rocks
Silicates dominate (95% of crust)
Quartz, Plagioclase feldspar, K-feldspar, Micas, Amphiboles, Pyroxenes, Clay
Carbonates are common
Evaporite minerals
Secondary minerals formed during weathering

42. Felsic Minerals Silicate minerals rich in silicon and aluminum
Relatively low densities
Low crystallization temperatures
Framework structures
Generally light colors
Feldspars
Potassium feldspar (~2.5 g/cm3)
Plagioclase feldspar (~2.6 g/cm3)
Quartz (2.65 g/cm3)
Mica – muscovite (2.8 g/cm3)

43. Feldspar Plagioclase K-feldspar (Ca,Na)(Al,Si)4O8 (Na,K)Al2Si3O8
CaAl2Si2O8
NaAl2Si3O8
(Na,K)Al2Si3O8
KAlSi3O8
NaAlSi3O8

44. Feldspar Why? Plagioclase K-feldspar (Ca,Na)(Al,Si)4O8
CaAl2Si2O8
NaAl2Si3O8
Ca and Na Ions exchange for one another
(Na,K)Al2Si3O8
KAlSi3O8
NaAlSi3O8
K and Na Ions exchange for one another
Why?

45. Feldspar Plagioclase K-feldspar (Ca,Na)(Al,Si)4O8 CaAl2Si2O8
Ca and Na Ions exchange for one another
Size and Charge Similar
(Na,K)Al2Si3O8
KAlSi3O8
K and Na Ions exchange for one another
Size and Charge Similar

46. Ionic Substituion: Size and Charge
Figure 02-25
Title:
How composition varies among feldspars.
Caption:
Feldspar minerals are aluminum-silicate minerals containing various amounts of sodium, potassium, and calcium. In some feldspars, sodium and potassium substitute for one another, because they have the same ion charge (+1), even though they are different sizes. A complete gradation from sodium-rich to calcium-rich compositions defines the plagioclase feldspars. Sodium and calcium ions are similar in size but have different charges. To compensate for the charge imbalance, aluminum substitutes for silicon at the same time that calcium substitutes for sodium.

47. Ionic sizes and charges

48. Feldspar Why? Plagioclase K-feldspar (Ca,Na)(Al,Si)4O8 CaAl2Si2O8
Ca and Na Ions exchange for one another
Size and Charge Similar
(Na,K)Al2Si3O8
KAlSi3O8
K and Na Ions exchange for one another
Size and Charge Similar
Feldspars are most common mineral in the oceanic and continental crust.
Why?

49. Quartz SiO2 Very little chemical substitution for Si (or oxygen)
But many different colors from trace concentrations and tiny flaws in crystals
Chemically unreactive
Made of light elements
Density g/cm3

50. 02_10.JPG Figure 02-10 Title: Why quartz has many colors. Caption:
All quartz specimens are almost entirely composed of silica (SiO2), but the presence of even minute amounts of other elements can change its color. The purest quartz is colorless, but traces of titanium account for the pink color of rose quartz, whereas iron make amethyst purple.

51. Mafic Minerals
Silicate minerals rich in magnesium (ma-) and iron (-fic)
Relatively high density and higher crystallization temperatures
Generally dark colors
Olivine (~4.0+ g/cm3)
Pyroxenes (~3.4 g/cm3)
Amphiboles (~3.4 g/cm3)
Mica – biotite (~ g/cm3)
Why are mafic minerals more dense
than felsic minerals?

52. Mafic Minerals Pyroxene (~3.4 g/cm3) Amphibole(~3.4 g/cm3)
Figure 02-26
Title:
Examples of iron- and magnesium-rich silicate minerals.
Caption:
Iron and magnesium substitute for one another, and in some cases also with calcium, within the crystal structures of the dark silicate minerals olivine, pyroxene, and amphibole.
Pyroxene
(~3.4 g/cm3)
Amphibole(~3.4 g/cm3)
Olivine (~4.0+ g/cm3)

53. Clay Minerals Sheet silicates similar to mica
Products of chemical weathering near the Earth’s surface
Usually microscopic crystals
Kaolinite
SEM photograph of clay crystals from the Watahomigi Formation in Andrus Canyon, Supai Group, Grand Canyon; x 20, U.S. Geological Survey Professional Paper 1173.

54. Where are these minerals found?
Continental crust
Plagioclase, K-feldspar, quartz, mica, amphibole, pyroxene
Oceanic crust
Plagioclase, pyroxene, olivine
Mantle
Olivine, Pyroxene
Core
Metallic iron

55. Nonsilicate Minerals Carbonates
Calcite - CaCO3
Dolomite - CaMg(CO3)2
Oxides - Hematite (Fe2O3) Magnetite (Fe3O4)
Sulfates - Gypsum - CaSO4-2H2O
Sulfides – Pyrite – FeS2
Halides - Halite - NaCl
Native Elements
Gold, Silver, Copper, Sulfur, and Carbon

56. Nonsilicate Minerals Carbonates Sedimentary solutions
Oxides - Hematite Magnetite
Lots of different rocks
Sulfates – Gypsum Sedimentary solutions
Sulfides – Pyrite Metallic ore deposits
Halides – Halite Sedimentary solutions
Native Elements
Gold, Silver, Copper, Sulfur, and Carbon

59. Cleavage versus Fracture
Figure 02-05
Title:
How minerals break.
Caption:
Broken mineral fragments are differently shaped than mineral crystals. Broken quartz fractures like glass into irregular, sharp fragments. Calcite breaks into regularly shaped pieces that have six planar sides with rhomb shapes. The planes defining the calcite pieces are cleavage planes, while the pieces are called cleavage fragments.

61. Sedimentary solutions
Crystallize directly from water
Carbonates
Gypsum
Halite

62. Granite What is a rock? Which minerals are mafic?
A naturally occurring combination of one or more minerals
Granite
Which minerals
are mafic?

64. More Physical Properties
Luster
The appearance of reflected light
Influenced by the bonding
Metallic luster, shines like metal
Non-metallic, ranging from bright to dull
fluorescence

65. Magnetism Acid (HCl) Characteristic of only a few minerals
Calcite (CaCO3)

66. Physical Properties Hardness Not Density Resistance to abrasion
Strength of atomic bonds holding solid together
Mohs hardness scale
Arbitrary relative numbers assigned to 10 common minerals
Scale is not linear

67. 02_03.JPG Figure 02-03 Title: Comparing the hardness of minerals.
Caption:
Scraping two minerals against one another tests their relative hardness. The quartz crystal remains unblemished, while the calcite is scratched and powdered, indicating that calcite is softer than quartz.

68. 02_04.JPG Figure 02-04 Title: How mineral hardness is defined.
Caption:
The Mohs hardness scale is a relative scale with values between 1 and 10 that simply rank minerals from softest to hardest. More quantitative measurement methods determine the absolute hardness of minerals. Calcite and quartz are four steps apart on Mohs scale, but quartz is more than 10 times harder than calcite. The black triangles show the Mohs hardness of common objects for comparison.

69. 02_23.JPG
Figure 02-23
Title:
Why diamond and graphite have different physical properties.
Caption:
Diamond and graphite consist only of carbon atoms, but their physical properties differ. Carbon atoms in diamond are closely spaced and share strong covalent bonds in all directions; this configuration produces the hardest mineral on Earth. The smooth crystal faces defining the external form of diamond coincide with planes of carbon atoms in the crystal structure. In graphite, however, carbon atoms are more widely spaced than in diamond and are strongly bonded only in two dimensions. The covalently bonded carbon sheets are weakly held together by van der Waals forces. The weakly linked sheets readily separate in graphite, accounting for its softness and its tendency to cleave readily into thin, scaly plates.

70. Physical Properties Hardness Mohs hardness scale
Resistance to abrasion
Strength of atomic bonds holding solid together
Mohs hardness scale
Arbitrary relative numbers assigned to 10 common minerals
Scale is not linear

71. Physical Properties Color Streak Most obvious property
Not diagnostic for ID purposes
Variations due to trace elements
Streak
Color of mineral powder
Diagnostic property

72. Hematite Colors & Streak

73. 02_08.JPG Figure 02-08 Title: Mineral streak colors. Caption:
Minerals softer than porcelain (about 6.5 on Mohs scale) leave a powdery residue, called streak, when scraped across a porcelain plate. Calcite streak is white, which is similar to the color of the mineral specimen. The iron mineral hematite always leaves a red-brown streak on a porcelain plate, even when the mineral specimen itself is not red-brown.

74. (quality of reflected light)

75. Physical Properties: Luster
The appearance of reflected light
Influenced by the type of bonding in the mineral
Metallic luster
Shines like metal
Non-metallic
Widely ranging from bright to dull

76. Physical Properties Magnetism Characteristic of only a few minerals
Iron bearing minerals
Magnetite
An important property of rocks in geophysical investigations of the Earth

77. 02_29.JPG Figure 02-29 Title: Magnetite is magnetic. Caption:
Magnetite is a strongly magnetic oxide mineral. This particular property distinguishes magnetite from other, similar-looking minerals.

78. 02_02.JPG Figure 02-02 Title: What do minerals look like? Caption:
Although many mineral samples appear shapeless, all minerals have distinctive crystal shapes. Calcite and quartz are two common minerals. Exceptional crystals of both minerals are transparent and six-sided, but as these drawings emphasize, they have different forms.

79. 02_07.JPG Figure 02-07 Title: Variations in mineral color. Caption:
Samples of quartz and calcite come in a variety of external forms and colors. One type of mineral can occur in a variety of colors, while different minerals can have the same color.