EARTH AND PLANETARY SCIENCES 101 Fall, 2002

THE WAY THE EARTH WORKS

MINERALOGY, ATOMIC STRUCTURE, SILICATE MINERALS, MINERAL PROPERTIES, MINERAL COMPOSITIONS

I. Minerals the Building Blocks of Geologic Materials (rocks)

A. Atomic structure (note handout on the packing of spheres)

1. Bonding

a. Ionic bonds are between SiO₄ tetrahedra, cations (e.g., K⁺ Ca⁺⁺ Fe⁺⁺ Fe⁺⁺⁺ Mg⁺⁺, etc.)

b. Covalent bonds important for individual SiO₄ tetrahedra

c. Van der Waals bonds

B. Definition of a Mineral

1. naturally occurring

2. solid

3. inorganic compound

4. definite composition (or definite range of compositions)

C. Glasses and their difference from minerals….

D. Silicates

(Minerals characterized by the SiO₄ tetrahedron joined in a particular two, three, or one-dimensional array. Make up the vast majority of the earth’s crust!! )

1. Isolated tetrahedra-- Olivines (dense, Fe,Mg solid solution ,high melting temperature (anhydrous, (mantle building mineral)

2. ring tetrahedra--relatively unimportant silicates (gems)

3. single chains --Pyroxenes (Fe,Mg,Ca solid solutions (anhydrous, moderate melting temperatures, mantle building mineral)

4. double chains -Amphiboles (Fe,Mg,Ca,K,Al complex chemistry (hydrous, moderate melting temperature, mineral common to crust and rare in mantle.)

5. layered - Micas, Clays (Fe,Mg,Al,K,Na,Ca) (hydrous)(low melting temperatures)

6.Framework silicates -Feldspars, Quartz -(all O's of SiO₄ tetrahedra are shared. Feldspars (K,Ca,NaAl (anhydrous (low to high melting temperatures (crude only)

Quartz (SiO₂) (anhydrous)high melting temperature (crude only)

E. Others

1. Carbonates C0₃^-2

2. Oxides O^-2

3. Sulfides S^{-1, -2}

II. Mineral Properties (readily visible)

A. Color

B. Streak

C. Luster

D. Hardness

E. Specific gravity (density)

F. Crystal form

G. Cleavage, Fracture

III. Other properties (more important)

A. Melting Temperature

B. Magnetism

C. Thermal conductivity

D. Electrical Conductivity