Earth Science, 10e Edward J. Tarbuck & Frederick K. Lutgens

Minerals: Building Blocks of Rocks Chapter 1 Earth Science, 10e

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  Mineraloid - lacks an orderly internal structure

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 Crystal form Luster Color Streak Hardness Cleavage

Mineral Identification 1.Color 2. Luster 3.Streak 4. Hardness 5. Cleavage 6. Fracture 7. Crystal form 8. Density 9. Specific gravity 10. Magnetism 11.Reaction to hydrochloric acid (HCl) 12.Taste 13. Fluorescence 14. Double refraction

The mineral quartz often exhibits good crystal form

Pyrite (fool’s gold) displays metallic luster

1.Color not always diagnostic (feldspar, quartz, fluorite) Feldspar can be green, pink white, gray, etc.

Three examples of perfect cleavage – fluorite, halite, and calcite

Cleavage Breakage along planes. Related to crystal structure 1 direction (muscovite, biotite) Muscovite (left) Biotite (right)

2 directions at 90° (feldspar, pyroxene) Pyroxene

3 directions at 90° (cubic) (halite, galena) Halite Galena

3 directions not at 90°(rhombohedral ) (calcite, dolomite) Cleavage fragments of calcite Cleavage fragments of dolomite

4 directions (octahedral) (fluorite) Cleavage fragments of fluorite Sphalerite 6 directions (sphalerite)

Minerals  Physical properties of minerals Fracture Specific gravity Other properties Taste Smell Elasticity Malleability

Fracture irregular breakage (no cleavage), breakage not along smooth planes Conchoidal fracture smooth curved fracture surfaces occurs in quartz, chert, obsidian, glass Rose quartz and obsidian lacks cleavage; they have conchoidal fracture

Conchoidal fracture

Minerals  Physical properties of minerals Other properties Feel Magnetism Double Refraction Reaction to hydrochloric acid

Double refraction Light passing through the mineral is split into two rays. Causes an optical "doubling" effect. Calcite Calcite has the optical property of double refraction. In the photos above, the same sample of calcite is used. It is rotated over a thin dark line. Examine how the appearance of he line changes in the different orientations of calcite.

Mineral Formation 1. Magma formation- cooling of hot molten rock material -Atoms lose energy and move closer together, patterns. 2. Liquid evaporation- minerals dissolved in liquids -Liquid evaporates, atoms of minerals stay & form crystals 3.Precipitation- alternate material in supersaturated solutions

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)

Minerals  Mineral groups Rock-forming silicates Most common mineral group Contain the silicon-oxygen tetrahedron Four oxygen atoms surrounding a much smaller silicon atom Combines with other atoms to form the various silicate structures

The silicate (SiO 4 ) -4 molecule

Common silicate minerals

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

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 Two types of feldspar are Orthoclase and Plagioclase Quartz – three-dimensional network of tetrahedra

Potassium feldspar

Plagioclase feldspar

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

Minerals  Mineral groups Nonsilicate minerals Major groups Sulfates Carbonates “Native” elements

Native Copper

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

Some common non-silicate 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 halite (salt) mine

The Bingham copper mine in Utah

End of Chapter 1