Minerals

MINERALS

What is a Mineral?What is a Mineral?

A mineral is a naturally formed inorganic crystalline solid A mineral is a naturally formed inorganic crystalline solid with a definite chemical composition and identifying with a definite chemical composition and identifying physical propertiesphysical properties naturally formednaturally formed

formed by geologic processes in nature, not by humansformed by geologic processes in nature, not by humans inorganicinorganic

was never alivewas never alive crystalline solidcrystalline solid

a solid composed of atoms arranged in a repeating orderly a solid composed of atoms arranged in a repeating orderly frameworkframework

definite chemical compositiondefinite chemical composition a homogeneous chemical compound with a chemical formulaa homogeneous chemical compound with a chemical formula

distinctive, identifying physical propertiesdistinctive, identifying physical properties

Definition

MINERAL

• Adalah zat padat yang terbentuk secara alami, memiliki komposisi kimia tertentu dan bentuk (kristal) spesifik

• Dalam perkembangannya, air dan minyak bumi diklasifikasikan pula sebagai mineral

• Dengan demikian, sumberdaya mineral mencakup semua bahan tambang baik padat maupun cair, dan air alami

Definition

• Mineral is a naturally occurring inorganic element or compound having orderly internal structure and characteristic chemical composition, crystal form, and physical properties

Pertanyaan:• Apakah lampu kristal tergolong mineral?• Bagaimana dengan tubuh kekurangan

mineral? Air mineral?

• Mineral is a structurally homogeneous solid of definite chemical composition, formed by the inorganic processes of nature.

Whitten, DGA and Brooks, JRV. 1977. The Penguin Dictionary of Geology. Middlesex: Penguin Books. p. 293.

Definition

• This definition includes ice as a mineral, but excludes coal, natural oil and gas. The only allowable exception to the rule that a mineral must be “solid” is native mercury (quicksilver), which is liquid.

• “Definite chemical composition” is not synonymous with ‘fixed or constant composition’, since many minerals have compositions which are variable between certain limits, which are defined in terms of end members: e.g. the composition of the common olivines is expressible in terms of the two compounds, Mg2SiO4 (forsterite) and

Fe2SiO4 (fayalite). The general rule is that minor

variations of composition which do not markedly alter fundamental properties are discounted

Definition

• “Structurally homogeneous” implies that the fundamental atomic structure is continuous and constant through the mineral unit, e.g. in silicates the silicon-oxygen lattice will be constant in characters, although the interstitial cations may vary in different parts of the lattice

• Although strictly of “organic origin”, the constituents of many limestones, siliceous rocks, and bedded phosphate deposits are treated as though they were true mineral species

Whitten, DGA and Brooks, JRV. 1977. The Penguin Dictionary of Geology. Middlesex: Penguin Books. p. 293-294.

Definition

MINERAL

Mineral ClassesMineral Classes

Silicate Mineral GroupSilicate Mineral Group

Non-silicate Mineral Non-silicate Mineral Group Group

Silicate Mineral Groups Silicate minerals (silicates) are composed of silica tetrahedra (SiO4

4-)

For silica tetrahedra to be stable, they must either: be balanced by positive ions, share oxygens with adjacent silica tetrahedra, or substitute one or more Al 3+ for Si 4+

Compositions of the silicates Mafic composition

Is rich in magnesium, iron, and/or calcium Intermediate composition

Is compositionally between mafic and felsic Is rich in feldspar and/or silica (quartz)

Felsic composition

Is rich in feldspar and/or silica (quartz) All the common rock-forming minerals are silicate mineral

The Silica TetrahedronThe Silica Tetrahedron

(composed of 4 oxygen atoms surrounding 1 silicon atom)(composed of 4 oxygen atoms surrounding 1 silicon atom)

Silicate Mineral Groups

Two Two IllustrationsIllustrations

of theof theSi–OSi–O44

TetrahedronTetrahedron


Single Island SilicatesSingle Island Silicates(ex.: olivine)(ex.: olivine)

Single Chain SilicatesSingle Chain Silicates(ex.: augite pyroxene)(ex.: augite pyroxene)


Single Chain Silicates: The Pyroxenes (e.g., augite)Single Chain Silicates: The Pyroxenes (e.g., augite)


Double Chain Silicates: The Amphiboles Double Chain Silicates: The Amphiboles (e.g., hornblende)(e.g., hornblende)


Sheet Silicates: The Micas Sheet Silicates: The Micas (e.g., biotite, muscovite, and the clays)(e.g., biotite, muscovite, and the clays)

Because of weak bonds,mica splits asily between “sandwiches”

Positive ions, sandwiches between two sheetssilicate layers

Sheet silicate structure

Example:Clay groupsMica groups


(O)

(Si)

(Al)

(Fe)

(Ca)

(Na)

(K)

(Mg)

The Common Rock-Forming Silicate MineralsThe Common Rock-Forming Silicate Minerals


Non-silicate Mineral Groups

Native CopperNative Copper

Non-silicate Mineral Groups

By crystallization from magma (molten rock material) By crystallization from magma (molten rock material) a saturation responsea saturation response

By crystallization (precipitation) from aqueous fluids By crystallization (precipitation) from aqueous fluids a saturation responsea saturation response

By chemical reaction with By chemical reaction with magmatic fluidsmagmatic fluids hydrothermal fluidshydrothermal fluids water during weatheringwater during weathering

By solid state transformations (metamorphism)By solid state transformations (metamorphism) changes crystal formchanges crystal form moves ions to new locationsmoves ions to new locations promotes growth along the edges of mineral grains (crystals) promotes growth along the edges of mineral grains (crystals)

at the expense of their neighboring mineral grainsat the expense of their neighboring mineral grains

How do minerals form?

Crystallization of Minerals in Cavities: GeodesCrystallization of Minerals in Cavities: Geodes


The Effect of Crowding on Crystal GrowthThe Effect of Crowding on Crystal Growth


PolymorphsPolymorphs

Polymorphs are minerals that have the same chemical Polymorphs are minerals that have the same chemical composition but a different crystal formcomposition but a different crystal form

Graphite and diamond polymorphs of carbonGraphite and diamond polymorphs of carbon Graphite forms at low temperature and pressure Graphite forms at low temperature and pressure Diamond forms at high temperature and pressure Diamond forms at high temperature and pressure

Quartz, stishovite, and coesite are polymorphs of SiOQuartz, stishovite, and coesite are polymorphs of SiO22

Quartz forms at low to medium temperature and pressureQuartz forms at low to medium temperature and pressure stishovite and coesite form at high pressure, such as that stishovite and coesite form at high pressure, such as that

associated with meteor impactsassociated with meteor impacts Andelusite, kyanite, and sillimanite are polymorphs of AlAndelusite, kyanite, and sillimanite are polymorphs of Al22SiOSiO55

Andelusite is the low temperature low pressure polymorphAndelusite is the low temperature low pressure polymorph Kyanite is the low temperature high pressure polymorphKyanite is the low temperature high pressure polymorph Sillimanite is the high temperature high pressure polymorphSillimanite is the high temperature high pressure polymorph


PseudomorphsPseudomorphs

Pseudomorphs are minerals that have the same crystal form but Pseudomorphs are minerals that have the same crystal form but a different chemical compositiona different chemical composition Limonite forms cubic pseudomorphs after pyriteLimonite forms cubic pseudomorphs after pyrite Quartz forms pseudomorphs after fluoriteQuartz forms pseudomorphs after fluorite


Rock Forming Minerals

Minerals: identification

QuestionsQuestions How can you identify minerals?How can you identify minerals? How do geologists identify How do geologists identify

minerals?minerals?

Identification of Minerals

Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals

1.1. Crystal formCrystal form2.2. ColorColor3.3. StreakStreak4.4. LusterLuster5.5. CleavageCleavage6.6. FractureFracture7.7. HardnessHardness8.8. Tenacity Tenacity 9.9. Specific gravitySpecific gravity10.10. TasteTaste11.11. MagnetismMagnetism12.12. Reaction with acidReaction with acid13.13. Striations Striations

CRYSTAL SYSTEM

• Regular: halite, diamond, pyrite

• Tetragonal: dolomite

• Trigonal: calcite

• Hexagonal: quartz

• Orthorhombic: ortho pyroxene

• Monoclinic: clyno pyroxene

• Triclinic: plagioclase

1. Crystal form 1. Crystal form Is a set of crystalline faces having a definite Is a set of crystalline faces having a definite

geometric relationship to one anothergeometric relationship to one another

GarnetGarnet

QuartzQuartz


Colors of ruby and sapphire, Colors of ruby and sapphire, varieties of corundum (Alvarieties of corundum (Al22OO33) )

2. Color2. Color Is due to visible wavelengths of light not absorbedIs due to visible wavelengths of light not absorbed Is the most obvious but least reliable property to use Is the most obvious but least reliable property to use

for identificationfor identification

Smoky quartz

Colors of Varieties of QuartzColors of Varieties of Quartz

Milky quartz

Amethyst

Citrine


Figure 1.8Figure 1.8

3. Streak3. Streak The color of a mineral in powder formThe color of a mineral in powder form


4.4. Luster Luster Is the intensity of light reflected from a surfaceIs the intensity of light reflected from a surface

Have a metallic lusterHave a metallic lusterHas a nonmetallic lusterHas a nonmetallic luster

Pyrite

Galena

Potassium feldspar


5. Cleavage 5. Cleavage Is breakage along planes of weaknessIs breakage along planes of weakness Is due to weak bonding between those planesIs due to weak bonding between those planes



Various Types of CleavageVarious Types of Cleavage

Pyramidal Cleavage Cubic Cleavage, and Rhombohedral Cleavage Pyramidal Cleavage Cubic Cleavage, and Rhombohedral Cleavage Displayed by Fluorite, Halite, and CalciteDisplayed by Fluorite, Halite, and Calcite

FluoriteFluoriteHaliteHalite

CalciteCalcite


Identifying Physical Properties of MineralsIdentifying Physical Properties of MineralsDistinguishing between Cleavage Planes and Crystal FacesDistinguishing between Cleavage Planes and Crystal Faces

•Cleavage Planes:Cleavage Planes: Repeated like a series Repeated like a series of step or terraces of step or terraces

•A crystal face:A crystal face: A single surface A single surface No repetitions of the No repetitions of the crystal face within crystal face within a crystal a crystal

6. Fracture 6. Fracture Is breakage in random directions Is breakage in random directions Is due to the absence of weak bonding between planesIs due to the absence of weak bonding between planes Conchoidal fracture yields scalloped edges like in broken glassConchoidal fracture yields scalloped edges like in broken glass


7. Hardness 7. Hardness Is the resistance to scratchingIs the resistance to scratching

Is based on the Moh’s ScaleIs based on the Moh’s Scale 1 talc1 talc 2 gypsum2 gypsum 3 calcite3 calcite 4 fluorite4 fluorite 5 apatite5 apatite 6 potassium feldspar (orthoclase)6 potassium feldspar (orthoclase) 7 quartz7 quartz 8 topaz8 topaz 9 corundum9 corundum 10 diamond10 diamond


Mohs Hardness

Scale


8. Tenacity 8. Tenacity resistance to breaking or bendingresistance to breaking or bending

9. Specific gravity: an expression of heaviness9. Specific gravity: an expression of heaviness

density of a substance density of a substance XX g/cm g/cm33

density of water 1 g/cmdensity of water 1 g/cm33

10. Taste 10. Taste Halite (rock salt) tastes saltyHalite (rock salt) tastes salty

11. Magnetism 11. Magnetism magnetite attracts a magnetmagnetite attracts a magnet


SGSG == == XX==

12. Reaction with acid 12. Reaction with acid minerals containing a COminerals containing a CO33 ion fizz (release CO ion fizz (release CO22) when ) when

in contact with hydrochloric acidin contact with hydrochloric acid

2HCl + CaCO2HCl + CaCO33 →→ Ca Ca2+2+ + 2Cl + 2Cl-- + H + H22O + COO + CO22

13. Reaction with acid Striations 13. Reaction with acid Striations Are saw-tooth lines present on crystal planes due to Are saw-tooth lines present on crystal planes due to

lamellar twinning (repetition) of crystals on that plane lamellar twinning (repetition) of crystals on that plane Striations are characteristic of plagioclase feldspar, Striations are characteristic of plagioclase feldspar,

calcite, dolomite, galena, and sphaleritecalcite, dolomite, galena, and sphalerite


Model of Silicates Structure

Date post:	24-Dec-2015
Category:	Documents
Upload:	permataisman
View:	3 times
Download:	1 times

Minerals

Documents