2. MINERALS

I. Introduction

  

-mineral- a naturally occurring, inorganic, crystalline solid, with a narrowly defined chemical composition, and characteristic physical properties.

 

-rock- a consolidated aggregate of minerals (or particles of other rocks).

 

-minerals are made up of elements. (ex. mineral halite made up of elements sodium and chlorine)

 

II. What does Matter Consist of?

 

-Matter: Anything that has mass and occupies space.

The three states of matter (phases): solids, liquids, and gases.

 

Elements and Atoms

 

-element- substance that can't be broken down into other substances by ordinary chemical means.  92 naturally occurring elements have been discovered (Table 2.3).

 

-atom- smallest part of an element that retains the properties of that element.  Cannot be split into by conventional means.

 

-atoms made of 3 kinds of particles: protons, neutrons, electrons.

 

1- proton- particles with a positive electric charge (has mass).

 

2- neutron- particle with no electric charge (electrically neutral) (has mass).

 

3- electron- particle with a negative electric charge (~no mass).  Orbit rapidly around the nucleus at specific distance.

 

-models of atoms (fig. 2.6):

 

-nucleus- central area of atom composed of protons and neutrons (~all mass here).

 

-shells- electron bearing layers that orbit the nucleus.

 

-The nucleus is only about 1/100,000 of the diameter of an atom.

 

-atomic number- number of protons in each atom (Table 2.3).

 

-atomic mass number- total number of neutrons and protons in an atom.

 

-isotopes- atoms containing same number of protons but different numbers of neutrons.  Some isotopes are radioactive (ex. Carbon 14) (Figure).

 

Bonding and Compounds

 

-bonding- process by which atoms are joined to other atoms.

 

-compound- substance formed when atoms of 2 or more different elements are bonded.

 

-ionic bonding- bonding due to the attraction between + charged ions and - charged ions; (electron transferred to other atom); the most common type of bonding in minerals (Ex. NaCl) (fig. 2.8a ; fig. 2.8b).

 

-covalent bonding- bonding due to the sharing of electrons by adjacent atoms (fig. 2.10).

 

-Metallic and van der Waals Bonds:
metallic: Extreme type of electron sharing (gold, silver)

VDW: Week (residual) attractive forces (between sheets of graphite

 

III. Minerals

-Most composed of 2 or more elements; Ex. Quartz  =  SiO2 (1 Si for every 2 O).

 

-A few minerals composed of just 1 element ; Ex.  Gold (Au), diamond (C);single elements= native elements

 

Mineral- a naturally occurring, inorganic, crystalline solid, with a narrowly defined chemical composition, and characteristic physical properties.

 

1) naturally occurring- not man made (diamonds, emeralds, rubies).

 

2) inorganic- excludes animal and vegetable matter (coal).

 

2) crystalline- atoms arranged in a regular 3-D framework; may exhibit crystal faces or cleavage;  glass- amorphous = w/o form. (Figure 2.11)

 

4) solid- no liquids or gasses (water not; ice is mineral).

 

5) narrowly defined chemical composition-chem. analysis will always give ~same chem. comp.  Some minerals have constant chemical composition (SiO2; NaCl)), others have a range of compositions, olivine (Mg,Fe)2SiO4

 

6) Physical Properties of Minerals- all minerals have physical properties that are ~constant for a given mineral and therefore aid in mineral identification; common physical properties include:

 

-color, luster, crystal form, cleavage, fracture, hardness, specific gravity, etc.

 

IV. Known Minerals

 

-over 3500 minerals known to exist, but only ~2 dozen are common

 

- only 8 elements make up over 98% of earth's crust (91 naturally occurring) (Table 2.4)

 

-by far most abundant elements are O and Si, usually combined with one or more of the other 6 elements.

 

-O & Si combine to form a group of minerals called the silicates (SiO4)-4

 

V. Mineral Groups

Ggeologists divide minerals into groups that have the same negatively charged ion or ion group; several groups (Table 2.5):

 

-silicates: 1/3 of all known minerals, but make up 95% of earth's crust; Ex. Quartz, SiO2

 

-other silicates contain one or more other elements; Ex. K-feldspar, KAlSi3O8; Olivine, (FeMg)2SiO4

 

-silica tetrahedron: basic building block of all silicate minerals (fig. 2.14)

 

-(SiO4)-4 not stable isolated; how make silica tetrahedron electrically neutral (stable)?

 

1)    add + charged ions (ex. Fe++, Mg++, Ca++, Al+++)

2)    share Oxygen atoms w/ other tetrahedra (usually a combination of 1 & 2)

 

-structure of silicate minerals: (fig. 2.15)

 

-4 different ways silica tetrahedrons are combined:

Isolated tetrahedra, Continuous chains, Continuous sheets, 3-D frameworks (fig 2.15).

 

-Silicate mineral divided into 2 groups depending on which +ions present:

 

1) ferromagnesian silicates; silicate minerals containing Fe, Mg, or both.

-dark colored and more dense (olivine, pyroxene, amphibole, biotite).

 

2) nonferromagnesian silicates; lack Fe and Mg

-lighter colored, less dense (quartz, K-feldspar, plagioclase, muscovite).

 

-Carbonate and Other mineral groups:

Carbonates; (CO3)-2; Calcium carbonate; Calcite; limestone.

Oxides; Hematite (Fe2O3); Magnetite (Fe3O4)

Sulfides; (S-2) Galena PbS

Sulfates; (SO4)-2 Gypsum (CaSO4.2H2O)

Halides; (Cl-1) Halite (NaCl) (Table 2.5).

 

VI. Mineral Identification

-     color & luster (metallic and nonmetallic)

-     crystal form (fig 2.11)

-     cleavage (fig 2.21) & fracture

-     hardness

-     specific gravity (ratio of weight / weight of equal volume of water)

 

VII. Rock forming minerals

 

-        Rocks are aggregates of one or more minerals.

-  rocks most commonly composed of silicates (Table 2.7).

 

VIII. Mineral Resources and Reserves

-resource- total concentration of material in such a form and amount that economic extraction is currently or potentially feasible; most nonrenewable because used up much faster than they can be replenished.

 

-classified as metallic (gold, iron), nonmetallic (sand, gravel, sulfur), or energy (uranium, coal, oil, natural gas) resources.

 

-reserve- the part of the resource that can be extracted economically.

-whether a deposit is a resource or a reserve depends on such things as concentration, transportation costs, labor costs, market price, and technological developments.