God Wholeness Rocks Minerals (Chemical bonds, Crystals) Chemical elements Atoms Something Nothing God

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 Percent by mass (%) Element Symbol 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 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 after Skinner and Porter, 1980

4.1. Elements Individual Person Atoms Ions

God Wholeness Rocks Minerals (Chemical bonds, Crystals) Chemical elements Atoms Something Nothing God

4.1. Elements Chemical bonds -Covalent bonds -Ionic bonds -Metallic bonds -Other bonds

4.1. Elements Covalent bonds strong bonds Diamond Source: Understanding Earth J.Grotzinger, T.H. Jordan, F. Press, R. Siever Source: Internet

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

4.1. Elements Metallic bonds complex bonds In a metallic bond, bonding electrons are delocalized overalattice(orasea)ofatoms. Pyrite Galena Antimonit Source: Internet

4.1. Elements Other bonds intermolecular bonds -Van der Waals bonds -Hydrogen bonds

God Wholeness Rocks Minerals (Chemical bonds, Crystals) Chemical elements Atoms Something Nothing God

Crystal means: - a homogenous solid -in which atoms are catchedin different chemical bonds - and its are arranged in an orderly, repeating, threedimensional 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 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) Monoclinic system Triclinic system

God Wholeness Rocks Minerals (Chemical bonds, Crystals) Chemical elements Atoms Something Nothing God

Mineral is: - a naturally occurring, solid crystalline substance, - 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 crystals grow larger, maintaining their crystal faces as long as they are free to grow and the time of cooling it's large. Themostlargemineralcrystalsforminopenspacesin rocks, such as fractures or cavities.

Source: Internet

Cubic system (izometric) Galena Halite Pyrite Diamond Fluorspar Source: Internet

Tetragonal system Cassiterite Scheelitee Zircon Stannite Source: Internet

Hexagonal system Apatite Beryl Zincite Graphite Source: Internet

Orthorhombic system Sulfur Baryte Topaz Olivine Source: Internet

Trigonal system (rhombohedral) Calcit Quartz Corundum Siderite Source: Internet

Monoclinic system Orthoclase Augit Gypsum Wolframite Source: Internet

Triclinic system Kaolinite Albite Chalcanthite Kyanite Source: Internet

The crystal faces of a mineral are the external expression of 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, crystal habit, specific gravity, transparency, reaction with acid, tenacity, taste and magnetic properties.

Colourandstreak Thecolourofamineral: -isthatseenonitssurfacebythenakedeye, - depend on the impurities present in light-coloured minerals, -is usually a general rather than specific guide to which mineral is present. The streak is the colour of the powdered mineral.

Colourandstreak Examples: Mineral Colour Streak Galena grey black Hematite black, red, brown reddish brown Olivine olive green, reddish white Orthoclase white grey, yellow, reddish white

Cleavageandfracture 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: 4.2. Identifying minerals Cleavageandfracture Mineral Number of cleavage directions Quartz no cleavage Micas 1 Pyroxenes 2 Amphiboles 2 Galena 3 Fluorite 4

Cleavageandfracture Fracture is: - a surface formed by breaking the mineral along a direction which is not a cleavage; - usually more irregular than a cleavage plane. Garnet Quartz Source: Internet

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 based Mohs, an Austrian mineralogist, devised a scale based on the ability of one mineral to scratch another.

Hardness Mohs scale Source: Geology for Civil Engineers A.C.McLean, C.D. Gribble

Lustre How the surface of a mineral reflects light gives it a characteristic luster. Luster iscontrolledbythe kindsofatomspresent and their bonding, both of which affect the way light passes through or is reflected by the mineral. Source: Internet

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

Cristalhabit The 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 is sometimes a clue to what it is, this shape or crystal habit is of use in the identification of some minerals. Source: Internet

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

Specificgravity The specific gravity or density of a mineral can be measured easily in a laboratory, provided the crystal is not too small. 2.00g/ccm 21.5g/ccm

Specificgravity - low specific gravity minerals include silicates, carbonates, sulphates and halides, - medium specific gravity minerals include metallic 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 canbeseenthroughacrystal. Source: Internet

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

Reactionwithacid When 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. Source: Internet

Tenacity Tenacity is a measure of how the mineral deforms whenitiscrushedorbent. Source: Internet

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

Tasteandmagneticproperties Taste and magnetic properties are diagnostic of a few 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.

4.3. Common minerals CLASS DESCRIPTION SOME MINERALS INCLUDED Element Includes native metals, inter-metallic elements, semimetals, non-metals, and natural alloys. antimony, bismuth, copper, diamond, carbides, electrum, gold, graphite, nitrides, phosphides, silicides, silver, sulfur

4.3. Common minerals Sulfide arsenides, antimonides, These are minerals that bismuthinides, bornite, have Sulfur (S) in their chalcocite, chalcopyrite, composition in the cinnabar, covellite, galena, form of S 2- as the major molybdenite, oorpiment, anion. Includes pentlandite, pyrite, realgar, Sulfosalts. selendides, sulfosalts, tellurides

Oxide Halide These are minerals that have oxygen in their composition that is not part of water. It also includes the hydroxide (OH) minerals Those Minerals that have Cl (chlorine), Br (bromine), F (fluorine), or I (iodine) at the end of their formula. 4.3. Common minerals bauxite, chromite, corrundum, hematite, Iice, ilmentite, magnetite, spinel, rutile, uranite, halite, fluorite, salamoniac, sylvite alum)

4.3. Common minerals Those minerals minerals containing the anion Carbonate(CO 3 )2. Also includes nitrate (NO 3 ) and borate (BO 3 ) containing minerals. aragonite, azurite, borax, calcite, dolomite, nalachite, niter, rhodochrosite, smithsonite, ulexite

Sulfate Phosphate Those minerals minerals containing the anion (SO 4 )2 4.3. Common minerals Includes any mineral with a tetrahedral unit (AO 3-4 ) where A can be Phosphorus (P), Antimony (Sb), Arsenic (As) or Vanadium (V). anglesite, anhydrite, barite, celestine, crocoite, chromate, gypsum, molybdate, xelenate, xulfite, tellurate, tungstate apatite, autunite, turquoise, nanadinite, nariscite, wavellite

4.3. Common minerals Includes minerals composed largely of silicon and oxygen, Silicate having the (SiO 2), with the addition of ions such as aluminum, magnesium, iron, and calcium. amphiboles, aquamarine, berlys, emerald, feldspars, garnets, goshenite, jade, 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