Minerals - Jurnalul lui Ştefan · PDF fileMinerals (Chemical bonds, Crystals) Rocks Wholeness...

Minerals

(Chemical bonds, Crystals)

Rocks

Wholeness

God

God

Nothing

Something

Atoms


Chemical elements

Theme 4.

Cristals and Minerals

4.1. Elements

4.2. Identifying minerals

4.3. Common minerals

4.1. Elements

Source: http://oxford-labs.com

4.1. Elements

Source: Understanding Earth –

J.Grotzinger, T.H. Jordan, F.

Press, R. Siever

4.1. Elements

Crust Globe

Oxygen O 45.20 29.50

Silicon Si 27.20 15.80

Aluminium Al 8.00 1.10

Iron Fe 5.80 34.46

Percent by mass (%)Element Symbol

after Skinner and Porter, 1980

Iron Fe 5.80 34.46

Calcium Ca 5.06 1.10

Magnesium Mg 2.77 12.70

Sodium Na 2.33 0.60

Potassium K 1.68 0.10

Other 1.96 5.64

4.1. Elements

Individual

Person

AtomsIons

Minerals


Rocks

Wholeness

God

God

Nothing

Something

Atoms


Chemical elements

4.1. Elements

Chemical bonds

-Covalent bonds

-Ionic bonds-Ionic bonds

-Metallic bonds

-Other bonds

4.1. Elements

Covalent

bonds –

strong bonds

Source: Understanding Earth – J.Grotzinger,

T.H. Jordan, F. Press, R. Siever

Source: Internet

Diamond

4.1. Elements

Ionic bonds – weak bonds

Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever

4.1. Elements

Ionic bonds – weak bonds

Source: Understanding Earth – J.Grotzinger,

T.H. Jordan, F. Press, R. Siever

Halite

4.1. Elements

Metallic bonds – complex bonds

In a metallic bond, bonding electrons are delocalized

over a lattice (or a sea) of atoms.

Source: Internet

Pyrite

AntimonitGalena

4.1. Elements

Other bonds – intermolecular bonds

-Van der Waals bonds

-Hydrogen bonds-Hydrogen bonds

Minerals


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Atoms


Chemical elements


Crystal means:

- a homogenous solid

- in which atoms are catched in different chemical

bonds

- and its are arranged in an orderly, repeating, three-

dimensional array.


All crystals possess certain elements of

symmetry.

The angles between the faces are the same in

the same type of crystal (perfect or imperfect).


Centre of symmetry:

- a crystal possesses when all its faces occur in

parallel pairs on opposite sides of the crystal.

Axis of symmetry:

- is a line through a crystal such that a complete- is a line through a crystal such that a complete

rotation of 360° about it produces more than one

identical view.

Plane of symmetry:

- divides the crystal into halves, each of which is a

mirror image of the other without rotation.


On the basis of the number and type of symmetry

elements present in naturally formed crystals, there

are seven crystal systems.

Cubic system

(izometric)

Tetragonal system

Hexagonal system


Orthorhombic system

Trigonal system

(rhombohedral)

Triclinic system

Monoclinic system

Minerals


Rocks

Wholeness

God

God

Nothing

Something

Atoms


Chemical elements


Mineral is:

- a naturally occurring, solid crystalline substance,

- generally inorganic,- generally inorganic,

- with a specific chemical composition.


Minerals form by the process of crystallization, in

which the atoms of a gas or liquid come together in

the proper chemical proportions and crystalline

arrangement.

During crystallization, the initially microscopic crystalsDuring crystallization, the initially microscopic crystals

grow larger, maintaining their crystal faces as long as

they are free to grow and the time of cooling it's

large.

The most large mineral crystals form in open spaces in

rocks, such as fractures or cavities.


Source: Internet


Cubic system (izometric)

Galena

Halite

Source: Internet

Pyrite

Fluorspar

Diamond


Tetragonal system

Cassiterite

Scheelitee

Source: Internet

Stannite

Zircon


Hexagonal system

Apatite

Zincite

Beryl

Source: Internet

Graphite


Orthorhombic system

Sulfur

Topaz

Baryte

Source: InternetOlivine


Trigonal system (rhombohedral)

Calcit

Source: Internet

Quartz

Siderite

Corundum


Monoclinic system

Orthoclase Augit

Source: Internet

Wolframite

Gypsum


Triclinic system

Kaolinite

Albite

Source: Internet

Kyanite

Chalcanthite


The crystal faces of a

mineral are the

external expression

of the mineral'sof the mineral's

internal atomic

structure.

Source: Internet


As well as crystallography, other important properties

are used to identify minerals, as follows:

• colour and streak,

• cleavage and fracture,

• hardness,

• lustre,lustre,

• crystal habit,

• specific gravity,

• transparency,

• reaction with acid,

• tenacity,

• taste and magnetic properties.


Colour and streak

The colour of a mineral:

- is that seen on its surface by the naked eye,

- depend on the impurities present in light-coloured

minerals,minerals,

-is usually a general rather than specific guide to

which mineral is present.

The streak is the colour of the powdered mineral.


Colour and streak

Mineral Colour Streak

Galena grey black

Examples:

Galena grey black

Hematite black, red, brown reddish brown

Olivine olive green, reddish white

Orthoclase white grey, yellow, reddish white


Cleavage and fracture

Most minerals can be cleaved along certain specific

crystallographic directions which are related to planes

of weakness in the atomic structure of the mineral.

These cleavage directions are usually parallel to one

of the crystal faces.

Calcite

Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble



Examples:

Mineral Number of cleavage directions

Quartz no cleavageQuartz no cleavage

Micas 1

Pyroxenes 2

Amphiboles 2

Galena 3

Fluorite 4



Fracture is:

- a surface formed by breaking the mineral along a

direction which is not a cleavage;direction which is not a cleavage;

- usually more irregular than a cleavage plane.

Quartz

Source: Internet

Garnet


Hardness

Hardness is a measure of the ease with which the

surface of a mineral can be scratched.

Mohs, an Austrian mineralogist, devised a scale basedMohs, an Austrian mineralogist, devised a scale based

on the ability of one mineral to scratch another.


Hardness – Mohs’ scale



Lustre

How the surface of a mineral reflects light gives it a

characteristic luster.

Luster is controlled by the kinds of atoms present andLuster is controlled by the kinds of atoms present and

their bonding, both of which affect the way light

passes through or is reflected by the mineral.

Source: Internet


Lustre



Cristal habitThe development of an individual crystal, or an

aggregate of crystals, to produce a particular external

shape depends on the temperature and pressure

during their formation.

Since the mode of formation of a mineral isSince the mode of formation of a mineral is

sometimes a clue to what it is, this shape or crystal

habit is of use in the identification of some minerals.

Source: Internet


Cristal habit



Specific gravityThe specific gravity or density of a mineral can be

measured easily in a laboratory, provided the crystal is

not too small.

2.00 g/ccm – 21.5 g/ccm


Specific gravity

- low specific gravity minerals include silicates,

carbonates, sulphates and halides,

- medium specific gravity minerals include metallic

ores such as sulphides and oxides,ores such as sulphides and oxides,

- high specific gravity minerals include native metallic

elements such as pure copper, gold and silver.


Transparency

Transparency is a measure of how clearly an object

can be seen through a crystal.

Source: Internet


Transparency



Reaction with acidWhen a drop of cold 10% dilute hydrochloric acid is

put on certain minerals, a reaction takes place.

In calcite (CaCO3), bubbles of carbon dioxide make the

acid froth, and in some sulphide ores, hydrogen

sulphide is produced.sulphide is produced.

Source: Internet


Tenacity

Tenacity is a measure of how the mineral deforms

when it is crushed or bent.

Source: Internet


Tenacity



Taste and magnetic properties

Taste and magnetic properties are diagnostic of a few

minerals.minerals.


Recapitulation – physical properties of minerals



There are more than 4000 known minerals.

CLASS DESCRIPTION SOME MINERALS INCLUDED

Includes native

metals, inter-metallic

antimony, bismuth, copper,

diamond, carbides, electrum,


Element

metals, inter-metallic

elements, semi-

metals, non-metals,

and natural alloys.

diamond, carbides, electrum,

gold, graphite, nitrides ,

phosphides, silicides, silver,

sulfur

These are minerals that

have Sulfur (S) in their

arsenides, antimonides,

bismuthinides, bornite,

chalcocite, chalcopyrite,


Sulfidecomposition in the

form of S2-as the major

anion. Includes

Sulfosalts.

cinnabar, covellite, galena,

molybdenite, oOrpiment,

pentlandite, pyrite, realgar,

selendides, sulfosalts,

tellurides

Oxide

These are minerals that

have oxygen in their

composition that is not

part of water. It also

includes the hydroxide

(OH) minerals

bauxite, chromite,

corrundum, hematite, Iice,

ilmentite, magnetite, spinel,

rutile, uranite,


(OH) minerals

Halide

Those Minerals that

have Cl (chlorine), Br

(bromine), F (fluorine),

or I (iodine) at the end

of their formula.

halite, fluorite, sal amoniac,

sylvite alum)

Carbonate

Those minerals minerals

containing the anion

(CO )2−. Also includes

aragonite, azurite,

borax, calcite, dolomite,

nalachite, niter,


Carbonate (CO3)2−. Also includes

nitrate (NO3) and borate

(BO3) containing minerals.

nalachite, niter,

rhodochrosite,

smithsonite, ulexite

Sulfate

Those minerals

minerals containing

the anion (SO4)2−

anglesite, anhydrite, barite,

celestine, crocoite,

chromate, gypsum,

molybdate, xelenate,

xulfite, tellurate, tungstate

Includes any mineral


Phosphate

Includes any mineral

with a tetrahedral

unit (AO43-) where A

can be Phosphorus

(P), Antimony (Sb),

Arsenic (As) or

Vanadium (V).

apatite, autunite,

turquoise, nanadinite,

nariscite, wavellite

Includes minerals

composed largely of

silicon and oxygen,

having the (SiO2) , with

amphiboles, aquamarine,

berlys, emerald, feldspars,

garnets, goshenite, jade,

kunzite, kyanite, micas,


Silicatehaving the (SiO2) , with

the addition of ions such

as aluminum,

magnesium, iron, and

calcium.

kunzite, kyanite, micas,

olivines, pyroxenes, quartz,

sodalite, talc, topaz,

tourmalines, staurolite,

zeolites


Common silicate minerals are polymorphs of silicate ions

and often other elements.


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