Minerals
(Chemical bonds, Crystals)
Rocks
Wholeness
God
God
Nothing
Something
Atoms
(Chemical bonds, Crystals)
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
(Chemical bonds, Crystals)
Rocks
Wholeness
God
God
Nothing
Something
Atoms
(Chemical bonds, Crystals)
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
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
(Chemical bonds, Crystals)
Rocks
Wholeness
God
God
Nothing
Something
Atoms
(Chemical bonds, Crystals)
Chemical elements
4.2. Identifying minerals
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.
4.2. Identifying minerals
All crystals possess certain elements of
symmetry.
The angles between the faces are the same in
the same type of crystal (perfect or imperfect).
4.2. Identifying minerals
4.2. Identifying minerals
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.
4.2. Identifying minerals
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
4.2. Identifying minerals
Orthorhombic system
Trigonal system
(rhombohedral)
Triclinic system
Monoclinic system
Minerals
(Chemical bonds, Crystals)
Rocks
Wholeness
God
God
Nothing
Something
Atoms
(Chemical bonds, Crystals)
Chemical elements
4.2. Identifying minerals
Mineral is:
- a naturally occurring, solid crystalline substance,
- generally inorganic,- generally inorganic,
- with a specific chemical composition.
4.2. Identifying minerals
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.
4.2. Identifying minerals
Source: Internet
4.2. Identifying minerals
Cubic system (izometric)
Galena
Halite
Source: Internet
Pyrite
Fluorspar
Diamond
4.2. Identifying minerals
Tetragonal system
Cassiterite
Scheelitee
Source: Internet
Stannite
Zircon
4.2. Identifying minerals
Hexagonal system
Apatite
Zincite
Beryl
Source: Internet
Graphite
4.2. Identifying minerals
Orthorhombic system
Sulfur
Topaz
Baryte
Source: InternetOlivine
4.2. Identifying minerals
Trigonal system (rhombohedral)
Calcit
Source: Internet
Quartz
Siderite
Corundum
4.2. Identifying minerals
Monoclinic system
Orthoclase Augit
Source: Internet
Wolframite
Gypsum
4.2. Identifying minerals
Triclinic system
Kaolinite
Albite
Source: Internet
Kyanite
Chalcanthite
4.2. Identifying minerals
The crystal faces of a
mineral are the
external expression
of the mineral'sof the mineral's
internal atomic
structure.
Source: Internet
4.2. Identifying minerals
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.
4.2. Identifying minerals
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.
4.2. Identifying minerals
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
4.2. Identifying minerals
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
4.2. Identifying minerals
Cleavage and fracture
Examples:
Mineral Number of cleavage directions
Quartz no cleavageQuartz no cleavage
Micas 1
Pyroxenes 2
Amphiboles 2
Galena 3
Fluorite 4
4.2. Identifying minerals
Cleavage and fracture
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
4.2. Identifying minerals
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.
4.2. Identifying minerals
Hardness – Mohs’ scale
Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble
4.2. Identifying minerals
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
4.2. Identifying minerals
Lustre
Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble
4.2. Identifying minerals
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
4.2. Identifying minerals
Cristal habit
Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble
4.2. Identifying minerals
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
4.2. Identifying minerals
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.
4.2. Identifying minerals
Transparency
Transparency is a measure of how clearly an object
can be seen through a crystal.
Source: Internet
4.2. Identifying minerals
Transparency
Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble
4.2. Identifying minerals
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
4.2. Identifying minerals
Tenacity
Tenacity is a measure of how the mineral deforms
when it is crushed or bent.
Source: Internet
4.2. Identifying minerals
Tenacity
Source: Geology for Civil Engineers – A.C.McLean, C.D. Gribble
4.2. Identifying minerals
Taste and magnetic properties
Taste and magnetic properties are diagnostic of a few
minerals.minerals.
4.2. Identifying minerals
Recapitulation – physical properties of minerals
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever
4.3. Common minerals
There are more than 4000 known minerals.
CLASS DESCRIPTION SOME MINERALS INCLUDED
Includes native
metals, inter-metallic
antimony, bismuth, copper,
diamond, carbides, electrum,
4.3. Common minerals
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,
4.3. Common minerals
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,
4.3. Common minerals
(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,
4.3. Common minerals
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
4.3. Common minerals
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,
4.3. Common minerals
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
4.3. Common minerals
Common silicate minerals are polymorphs of silicate ions
and often other elements.
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever
4.3. Common minerals
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever
4.3. Common minerals
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever
4.3. Common minerals
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever
4.3. Common minerals
Source: Understanding Earth – J.Grotzinger, T.H. Jordan, F. Press, R. Siever