Earth Science, Earth Science, 12e12e
Minerals: Building Minerals: Building Blocks of RocksBlocks of Rocks
Chapter 2Chapter 2
Minerals: the building Minerals: the building blocks of rocks blocks of rocks
Definition of a mineral • Natural• Inorganic• Solid• Possess an orderly internal structure of atoms • Have a definite chemical composition
Mineraloid – lacks an orderly internal structure
Composition and Composition and structure of minerals structure of minerals
Elements • Basic building blocks of minerals • Over 100 are known
Atoms• Smallest particles of matter • Have all the characteristics of an element
Periodic Table of the Periodic Table of the ElementsElements
Figure 2.4
How atoms are constructed How atoms are constructed
Nucleus – central part of an atom that contains • Protons – positive electrical charges • Neutrons – neutral electrical charges
Energy levels, or shells • Surround nucleus • Contain electrons – negative electrical
charges
Simplified view of the atomSimplified view of the atom
Figure 2.5
How atoms are constructed How atoms are constructed
Atomic number is the number of protons in an atom’s nucleus
Bonding of atoms • Forms a compound with two or more
elements • Ions are atoms that gain or lose electrons
Isotopes • Have varying number of neutrons
How atoms are constructed How atoms are constructed
Isotopes • Have different mass numbers – the sum of the
neutrons plus protons • Many isotopes are radioactive and emit
energy and particles
Minerals Minerals
Physical properties of minerals • Habit• Luster• Color• Streak• Hardness• Cleavage
The mineral quartz often The mineral quartz often exhibits good crystal shapeexhibits good crystal shape
Figure 2.21
Pyrite (fool’s gold) displays Pyrite (fool’s gold) displays metallic luster metallic luster
Figure 2.11
Figure 2.13
Mohs scale of hardness
Three examples of cleavage –Three examples of cleavage –halite, calcite, and fluoritehalite, calcite, and fluorite
Figure 2.15 B
Minerals Minerals
Physical properties of minerals • Fracture• Specific gravity• Other properties
• Taste• Smell• Elasticity• Malleability
Conchoidal fractureConchoidal fracture
Figure 2.16
Minerals Minerals
Physical properties of minerals • Other properties
• Feel• Magnetism• Double refraction• Reaction to hydrochloric acid
Minerals Minerals
A few dozen minerals are called the rock-forming minerals • The eight elements that compose most rock-
forming minerals are oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg)
• Most abundant atoms in Earth’s crust are oxygen (46.6% by weight) and silicon (27.7% by weight)
Composition of Composition of continental crustcontinental crust
Figure 2.19
Minerals Minerals
Mineral groups • Rock-forming silicates
• Most common mineral group • Contain the silicon-oxygen tetrahedron (molecule)
• Four oxygen atoms surrounding a much smaller silicon atom
• Combines with other atoms to form the various silicate structures
The silicate (SiOThe silicate (SiO44))4–4–
moleculemolecule
Figure 2.20
Minerals Minerals
Mineral groups • Rock-forming silicates
• Groups based on tetrahedral arrangement • Olivine – independent tetrahedra • Pyroxene group – tetrahedra are arranged in
chains• Amphibole group – tetrahedra are arranged in
double chains
Hornblende – a member of Hornblende – a member of the amphibole groupthe amphibole group
Figure 2.21
Minerals Minerals
Mineral groups • Rock-forming silicates
• Groups based on tetrahedral arrangement • Micas – tetrahedra are arranged in sheets
• Two types of mica are biotite (dark) and muscovite (light)
• Feldspars – Three-dimensional network of tetrahedra
Minerals Minerals
Mineral groups • Rock-forming silicates
• Groups based on tetrahedral arrangement • Feldspars
• Two types of feldspar are Orthoclase and Plagioclase
• Quartz – three-dimensional network of tetrahedra
Potassium feldsparPotassium feldspar
Figure 2.21
Minerals Minerals
Mineral groups • Rock-forming silicates
• Feldspars are the most plentiful mineral group • Crystallize from molten material
• Nonsilicate minerals • Major groups
• Oxides• Sulfides
Minerals Minerals
Mineral groups • Nonsilicate minerals
• Major groups• Sulfates• Carbonates• “Native” elements
Common nonsilicate Common nonsilicate mineral groupsmineral groups
Table 2.1
Minerals Minerals
Mineral groups • Nonsilicate minerals
• Carbonates• A major rock-forming group• Found in the rocks limestone and marble
• Halite and gypsum are found in sedimentary rocks• Many have economic value
Minerals Minerals
Mineral resources • Reserves are already identified deposits• Ores are useful metallic minerals that can be
mined at a profit • Economic factors may change and influence a
resource
An underground An underground halite (salt) minehalite (salt) mine
Figure 2.22