Earth Science, 12eMinerals: Building Blocks of Rocks Chapter 2

Minerals: the building blocks of rocks Definition of a mineral NaturalInorganicSolidPossess an orderly internal structure of atoms Have a definite chemical compositionMineraloid lacks an orderly internal structure

Composition and structure of minerals Elements Basic building blocks of minerals Over 100 are known AtomsSmallest particles of matter Have all the characteristics of an element

Periodic Table of the Elements Figure 2.4

How atoms are constructed Nucleus central part of an atom that contains Protons positive electrical charges Neutrons neutral electrical chargesEnergy levels, or shells Surround nucleus Contain electrons negative electrical charges

Simplified view of the atomFigure 2.5

How atoms are constructed Atomic number is the number of protons in an atoms 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 Isotopes Have different mass numbers the sum of the neutrons plus protons Many isotopes are radioactive and emit energy and particles

Minerals Physical properties of minerals HabitLusterColorStreakHardnessCleavage

The mineral quartz often exhibits good crystal shapeFigure 2.21

Pyrite (fools gold) displays metallic luster Figure 2.11

Figure 2.13Mohs scale of hardness

Three examples of cleavage halite, calcite, and fluoriteFigure 2.15 B

Minerals Physical properties of minerals FractureSpecific gravityOther propertiesTasteSmellElasticityMalleability

Conchoidal fractureFigure 2.16

Minerals Physical properties of minerals Other propertiesFeelMagnetismDouble refractionReaction to hydrochloric acid

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 Earths crust are oxygen (46.6% by weight) and silicon (27.7% by weight)

Composition of continental crustFigure 2.19

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 (SiO4)4 moleculeFigure 2.20

Minerals Mineral groups Rock-forming silicates Groups based on tetrahedral arrangement Olivine independent tetrahedra Pyroxene group tetrahedra are arranged in chainsAmphibole group tetrahedra are arranged in double chains

Hornblende a member of the amphibole groupFigure 2.21

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 Mineral groups Rock-forming silicates Groups based on tetrahedral arrangement FeldsparsTwo types of feldspar are Orthoclase and PlagioclaseQuartz three-dimensional network of tetrahedra

Potassium feldsparFigure 2.21

Minerals Mineral groups Rock-forming silicates Feldspars are the most plentiful mineral group Crystallize from molten material Nonsilicate minerals Major groupsOxidesSulfides

Minerals Mineral groups Nonsilicate minerals Major groupsSulfatesCarbonatesNative elements

Common nonsilicate mineral groupsTable 2.1

Minerals Mineral groups Nonsilicate minerals CarbonatesA major rock-forming groupFound in the rocks limestone and marble Halite and gypsum are found in sedimentary rocksMany have economic value

Minerals Mineral resources Reserves are already identified depositsOres are useful metallic minerals that can be mined at a profit Economic factors may change and influence a resource

An underground halite (salt) mineFigure 2.22