Lecture 2 - Geology

8/3/2019 Lecture 2 - Geology

1/11

MINERAL NOTIONS

The 2nd Course


2/11

The mineralogy is the science which studies the chemistry and

crystallographic structure of minerals. Knowing the names and important

characteristics of the most common elements and minerals is essential for

understanding how they combine forming the rocks of the earth.

Rock is naturally formed, consolidated material composed of grains of one

or more minerals.

The mineral in the geological sense of the term is a substance which

must satisfy five conditions:- to be a crystalline solid

- to occure naturally

- to be inorganic

- to have a definite chemical composition

- to have characteristic physical properties.

Each mineral is composed of certain chemical elements in a remarkablyorderly arrangement. The arrangement and characteristics of atoms

control the physical properties of minerals.

Most minerals are crystalline. A crystalline substance is one in which

the atoms are arranged in, regularly repeating orderly pattern.


3/11

Model of crystal structure of halite (Na Cl)

The internal structure is crystalline and the internal particles (ions, atoms or

molecules) are arranged in all the three dimensions of the space, forming a

3D network.

The chemical composition of any mineral can be expressed as a chemical

formula. The chemical analysis can aid the identification of minerals.

There are 32 classes and

7 systems of crystallization.

Chlorine (Cl)

Sodium (Na)


4/11

Crystallization systems

1.

2.

3.

4.

5.

6.

7.

Cubic (isometric)

monoclinic

tetragonalorthorhombic

triclinic

hexagonal

Rhomboedric(trigonal)


5/11

Classification of the minerals

Genetical minerals are formed:-by crystallization of magma the igneous minerals

Ex. Sulfides,oxides, native elements

-when the temperature and/or the pressure become high + chemistry of fluidsmetamorphic minerals

Ex. Clorite, talc, graphyte, biotite, Feldspar (Fp),

Pyroxene (Px)

-by weathering/alteration of preexisting minerals, transport and

deposition (in depositional environments)

sedimentary minerals

Ex. Calcite, salt, gypsum, anhydrite


6/11

Minerals classification after:

- How is made - the importance inside the rock

- color - chemical composition

How is made - endogeneformed inside of the earth (igneous and

methamorphic minerals)

- exogene formed outside of the earth crust

(sedimentary minerals)

The importance inside the rock - principalallways present in the rock,in high quantities cuartz, Fp

- accessoryallways present in the rock, in

lower quantities magnetite, hematite

- accidental sometimes present, in lower

quantities - they give the variety of the rock sienite with nefeline

Chemical composition -8 classes

1. Native elements 5. Carbonates

2. Sulfides 6. Sulfates

3. Oxides and hydroxides 7. Phosphates

4. Halides 8.Silicates

Olivine group

Amphibole group

Pyroxene group

Mica groupFeldspar group


7/11

CHEMICAL-STRUCTURAL CLASSIFICATION OF MINERALS

1.Native elements about 30 chimical natural elements

-metals si metaloids

Au, Ag, Cu, Pt S, C - Graphyte (H)- covalent connection (xy)

- Van der Waals connection (z)

- Diamond (C) covalent connections

2. Sulfides contain natural combinations of sulphur with different metals

Fe S2 - pyrite Cu Fe S2 chalcopyrite

Pb S - galena (lead sulfide)

Zn S - sphalerite (a zinc sulfide)

Obs. They form metallic depos

its (ore)

3. Oxides and hydroxides contain the most simple compounds of

metals and metaloids whith the oxygen and the hydroxile group (OH)-

Fe3 O4 magnetite Fe2 O 3 hematite

Al2 O3 -corundum

Obs. They form exploited deposits (ore)


8/11

7.Phosphates

+ H2O

4. Halides

- natural combinations of halogenes( F, Cl, Br, I) with differerents metals

Obs. They are soluble minerals (in water)

Na Cl halite K Cl silvine CaF2 fluorine

5. Carbonates

-contain mineral salts of oxigenate carbonic acid (H2CO3) to Ca, Mg, Fe,

Pb, Ba, Zr, Mn

Ca CO3 calcite Ca CO3 aragonite Ca Mg CO3 dolomiteRhomboedric Rhombic6. Sulfates

- natural salt of sulfuric acid

Obs. They are soluble minerals (in water)

Ca SO4 2H2O gypsum Ca SO4 Ca SO4 2H2 O(anhydrite) (gypsum)

-They have specific the anion

[PO4 ]3-

[Ca 5 (PO4)3(OH,F,Cl)] - apatite


9/11


10/11

8.3. Mica group

Sheet silicate structure-when each tetrahedron shares three oxygen ions

Obs. The sandwiched structure give a perfect cleavage

-mica group- muscovite (colorless, transparent or white-biotite (black, dark colored-iron/ magnesium-bearing mica)

-chlorite group

-clay group (Al hydro silicate)

- kaolinite

- montmorillonite

Obs. They are expansive minerals, if water

meolecule are adsorbed into the spaces between

silicate layers. It result a large increase in volume.

8.4. Feldspar group

Framework silicate structure - when all the four

oxygen ions are shared by adjacent tetrahedrons

-Silica group quartz, calcedony agate

-Feldspar group- Orthoclase, Plagioclase


11/11

Lecture 2 - Geology

Documents

Transcript of Lecture 2 - Geology