Earth Science, 13e Tarbuck & Lutgens

Matter and Minerals Earth Science, 13e Chapter 2 Stanley C. Hatfield Southwestern Illinois College

Minerals: the building blocks of rocks Definition of a mineral Natural Inorganic Solid Possess an orderly internal structure of atoms Have a definite chemical composition Rock – any naturally occurring solid mass of mineral or mineral-like matter

Composition and 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 elements

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 atom

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 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 Habit – common crystal shape Luster – appearance in reflected light Color Streak – color of mineral in powdered form Hardness – ability to resist scratching or abrasion Cleavage – tendency to break along planes of weak bonding

Good crystals of the mineral pyrite

Galena displays metallic luster

Mohs scale of hardness

Minerals Physical properties of minerals Fracture – random pattern of breakage Specific gravity – mineral density Other properties Taste Smell Elasticity Malleability

Conchoidal fracture

Minerals Physical properties of minerals Other properties Feel Magnetism Double Refraction Reaction 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 Earth’s crust are oxygen (46.6% by weight) and silicon (27.7% by weight)

Composition of continental crust

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 molecule

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

Hornblende – a member of the amphibole group © 2012 Pearson Education, Inc.

Minerals Mineral groups Rock-forming silicates Groups based upon 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 upon tetrahedral arrangement Feldspars – most abundant group of minerals in Earth’s crust Quartz – three-dimensional network of tetrahedra

Potassium feldspar © 2012 Pearson Education, Inc.

Minerals Mineral groups Nonsilicate minerals Major groups Oxides Sulfides Carbonates Halides Native elements

Common nonsilicate mineral groups © 2012 Pearson Education, Inc.

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 Mineral resources Mineral resources are occurrences of useful minerals that will eventually be extracted Ore deposits are concentrations of metallic minerals that can be mined at a profit Economic factors may change and influence a resource

An underground halite (salt) mine

End of Chapter 2