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Text lesson

Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering

Biology & Geology

Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering

Overview

Overview

  • Define a mineral and explain the chemical groups of minerals.
  • Compare the crystal systems and describe the optical and cohesive properties of minerals.
  • Classify rocks into igneous, sedimentary and metamorphic and explain how each forms.
  • Follow the rock cycle, including weathering, and its stages.

🌳 Concept tree

Lesson 2Rock Cycle, Minerals, Crystallography and Weathering
├── 1 Mineralsimportance and definition

│ ├── Man and minerals

│ ├── Minerals and rocks

│ └── Definition

├── 2 Formation and chemical groups of minerals

│ ├── Formation

│ ├── Elements of the crust (weight percentage)

  • │ ├── Chemical groups of minerals (from the most common to the least)
  • │ └── How many minerals?
  • ├── 3 Crystallography crystal structure and crystal systems

│ ├── Crystal structure

│ ├── Elements used to study crystals

│ ├── Systems with three axes

│ └── Systems with four axes

├── 4 Optical properties of minerals

│ ├── Luster

│ ├── Colour

│ ├── Streak

│ └── Play of colour

├── 5 Cohesive properties of minerals

│ ├── Hardness

│ ├── Cleavage

│ ├── Malleability and ductility

│ └── Other properties

├── 6 Rocks and their three types

├── 7 Igneous rocks

│ ├── Formation

│ ├── Bowen's reaction series

│ ├── Classification by mineral composition

  • │ ├── Classification by place of crystallization and texture

│ └── Shapes of igneous bodies in nature

├── 8 Sedimentary rocks

│ ├── Formation

│ ├── Characteristics

│ ├── Types by mode of formation

  • │ └── Energy resources in organic sedimentary rocks

├── 9 Metamorphic rocks

│ ├── Formation

│ ├── Massive metamorphic rocks

│ └── Foliated metamorphic rocks

├── 10 Weathering

│ └── Definition and types

└── 11 The rock cycle

├── James Hutton and the cycle

└── Stages

Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 1 / 13
1 Minerals: importance and definition

1 Minerals: importance and definition

Man and minerals

  • Early man coloured cave walls with minerals such as red and yellow ochre (hematite and limonite) and made pottery from clay after discovering fire.
  • The ancient Egyptians used coloured minerals and stones such as amethyst, malachite, emerald and turquoise for ornament.
  • Uses today calcite in the cement industry, quartz in glass, magnetite and hematite in steel, and feldspar in ceramics.
Comparison aspectMain ideaKeywords
The crust is made of three types of rock
  • igneous
  • sedimentary and metamorphic
igneoussedimentarymetamorphic
Most rocks are an aggregate of minerals (granite
  • quartz
  • feldspar and mica)
  • few are made of one mineral (limestone: calcite
  • CaCO3)
quartzfeldsparmicamade
•A rock consists of a group of minerals that share some common propertiesrockconsistsgroupminerals
  • A mineral is the basic natural unit from which a rock is formed.
  • For the mineralogist, a mineral is a solid, inorganic, naturally occurring substance with a definite chemical composition and a distinct crystalline form (a distinct atomic structure).
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 2 / 13
2 Formation and chemical groups of minerals

2 Formation and chemical groups of minerals

Formation

  • Minerals are formed from the known elements.
  • Some minerals consist of one element gold, sulphur, copper, graphite and diamond (both carbon).
  • Most minerals consist of two or more elements bonded in a stable compound, such as quartz (silicon dioxide) and calcite (calcium carbonate).
  • Although more than a hundred elements are known, eight elements make up more than 98.5% by weight of the crust.
  1. Oxygen 46.6%, silicon 27.7%, aluminium 8.1%, iron 5.0%.
  2. Calcium 3.6%, sodium 2.8%, potassium 2.6%, magnesium 2.1%.
  3. 1.5%.
Comparison aspectMain ideaKeywords
Silicates
  • quartz
  • orthoclase
  • plagioclase
  • mica
  • amphibole
  • pyroxene
  • olivine
quartzorthoclaseplagioclasemica
Carbonates
  • calcite
  • dolomite
calcitedolomite
Oxides
  • hematite
  • magnetite
hematitemagnetite
Sulphides
  • pyrite
  • galena
  • sphalerite
pyritegalenasphalerite
Sulphates
  • gypsum
  • anhydrite
  • barite
gypsumanhydritebarite
Native elements
  • gold
  • copper
  • graphite
  • sulphur
  • diamond
goldcoppergraphitesulphur
  • More than two thousand minerals are known, most in small amounts.
  • The common minerals and the economic minerals together do not exceed about two hundred.
  • The rock-forming minerals are only a few tens, in a few groups; the most famous group is the silicates.
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 3 / 13
3 Crystallography: crystal structure and crystal systems

3 Crystallography: crystal structure and crystal systems

Crystal structure

  • The atoms of a mineral are arranged in an orderly way, giving the crystal form.
  • A crystal is a solid geometric body with flat outer surfaces called crystal faces.
  • Example halite (rock salt, NaCl) forms when Na+ and Cl− ions combine in a repeated pattern, giving a cubic crystal.
  • The crystal system controls the shape of the mineral and its physical and chemical properties.
Comparison aspectMain ideaKeywords
Crystal axisa line through the centre of the crystal; when the crystal rotates around it, faces, edges or angles repeat two or three times. Axes are written a,b,c when their lengths differ and a1,a2,a3 when equal.linethroughcentrerotates
Angles between the axeswritten α,β,γ.written
Plane of symmetrya plane that divides the crystal into two identical halvesdividescrystalidenticalhalves
Crystal system Axes Angles Symmetry planes
Cubic a1=a2=a3 α=β=γ=90∘
  • Vertical
  • horizontal and inclined
  • the most symmetric system
Tetragonal a1=a2≠c α=β=γ=90∘ Vertical and horizontal
Orthorhombic a≠b≠c α=β=γ=90∘ Vertical and horizontal
Monoclinic a≠b≠c α=γ≠β (two axes perpendicular, one inclined) Only one; most minerals belong to this system
Triclinic a≠b≠c α≠β≠γ None
Comparison aspectMain ideaKeywords
Hexagonal
  • three horizontal axes of equal length crossing at equal angles
  • they are perpendicular to a fourth axis of a different length. The fourth (vertical) axis has hexagonal symmetry. It has vertical and horizontal planes of symmetry
threehorizontalaxesequal
Trigonal
  • three equal horizontal axes crossing at equal angles
  • the fourth axis is perpendicular to their plane and has three-fold symmetry. It has no horizontal plane of symmetry
threeequalhorizontalaxes
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 4 / 13
4 Optical properties of minerals

4 Optical properties of minerals

  • Geologists first use apparent physical properties to identify a mineral in the field.
  • Optical properties depend on the interaction between light falling on the mineral and the light reflected from its surface.
Lusteris the ability of a mineral to reflect the light falling on it.
Metallic lusterthe mineral looks bright like a metal, for example pyrite, galena and gold.
Non-metallic lustervitreous (glassy) in quartz and calcite; pearly in feldspar; dull or earthy in kaolinite.
Comparison aspectMain ideaKeywords
Colourdepends on the wavelengths of the light reflected from the surfacedependswavelengthslightreflected
•
  • It is the most obvious property but is not reliable
  • because impurities or a change in composition change the colour
mostobviouspropertyreliable
Quartz
  • rose quartz (manganese impurity)
  • amethyst (iron oxide impurity)
  • milky quartz (tiny gas bubbles)
  • pure quartz transparent and colourless (rock crystal)
rosemanganeseimpurityamethyst
•Sphalerite (zinc sulphide) is yellowish and turns brown when a little iron replaces zincSphaleritezincsulphideyellowish
Some minerals have a fixed true (native) colouryellow sulphur and green malachite (hydrated copper carbonate)yellowsulphurgreenmalachite
Comparison aspectMain ideaKeywords
Streak
  • is the colour of the powder of a mineral
  • obtained by scratching it on an unglazed porcelain plate
colourpowdermineralobtained
•
  • It stays constant even when the mineral colour changes with impurities
  • so it is a reliable property
staysconstantevenmineral
Hematite
  • dark grey or red crystals
  • red streak
darkgreycrystalsstreak
Pyrite
  • golden colour
  • black streak
goldencolourblackstreak
Quartz
  • many colours
  • white streak
manycolourswhitestreak
  • The colour seems to change when the mineral is moved before the eye. It characterises precious ornamental stones.
  • Diamond splits light into red and violet.
  • Precious opal shows spangling, a rippling luster that depends on the viewing direction.
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 5 / 13
5 Cohesive properties of minerals

5 Cohesive properties of minerals

Hardness

  • Hardness is the ability of a mineral to resist scratching; a harder mineral scratches a softer one.
  • It is measured numerically on Mohs’ scale:
Hardness 1 2 3 4 5 6 7 8 9 10
Mineral Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond
  • Common tools human fingernail (about 2.5), copper coin (3.5), window glass (5.5) and streak plate (6.5).
  • In the field or lab, sets of hardness pens made of alloys, or everyday objects of known hardness, are used.
Cleavageis the ability of a mineral to split along flat surfaces that represent weaker planes.
One directionmica splits into thin sheets (flaky cleavage); graphite has good basal cleavage.
Several directionshalite and galena have perfect cubic cleavage; calcite has rhombohedral cleavage.
No cleavagequartz and chert (flint) break with a conchoidal fracture.
  1. The ease of beating a mineral into thin sheets or drawing it into wires
  2. as in gold
  3. silver and copper.
Specific gravitygalena 7.5 and gold 19.3.
Magnetic propertymagnetite is attracted by a magnet.
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 6 / 13
6 Rocks and their three types

6 Rocks and their three types

  • A rock is a natural solid body made of a number of minerals combined in different ratios, and sometimes of one mineral only.
  • According to origin, rocks are igneous, sedimentary and metamorphic.
Point of comparison Igneous rocks Sedimentary rocks Metamorphic rocks
Structure Massive, crystalline Stratified (layered), rarely crystalline Foliated or massive, crystalline
Porosity Non-porous Often porous Non-porous
Fossils None Often contain fossils May contain deformed fossils
Origin Cooling of magma or lava
  • Weathering
  • transport
  • deposition
  • lithification
Heat and pressure acting on existing rocks
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 7 / 13
7 Igneous rocks

7 Igneous rocks

Formation

  • Igneous rocks are the first rocks to form on the crust; all other rocks come from them, so they are called the "mother rocks" or primary rocks.
  • They form by cooling and crystallization of molten magma (inside the Earth) or lava (on the surface) as its temperature falls.
  • Magma is a viscous liquid containing the eight main elements of the silicate minerals as ions, plus gases (mainly water vapour), held under high pressure in the asthenosphere.
  • Bowen’s experiments show that, as the magma cools, crystallization starts with minerals rich in iron, magnesium and calcium.
  • Then the magma becomes richer in sodium and potassium, and its silicon content rises in the last stages.
  • Six groups of minerals crystallize olivine (first), pyroxene, amphibole, feldspar (plagioclase and orthoclase), mica (biotite and muscovite) and quartz (last).
Comparison aspectMain ideaKeywords
Ultrabasic (ultramafic)silica less than 45%; the first rocks to crystallize; dark, rich in olivine and pyroxene, with a little calcium-rich plagioclase. Examples: plutonic peridotite and volcanic komatiite.silicalessfirstrocks
Basic (mafic)silica 45% to 55%; crystallize above 1100∘C; rich in iron, magnesium and calcium minerals, so black. Examples: plutonic gabbro, dolerite (porphyritic texture) and basalt, the most famous and used for road paving.silicacrystallizeabove1100
Intermediatesilica 55% to 66%; plagioclase feldspar, amphibole, mica, quartz and some potash feldspar; crystallize at moderate temperature, colours between light and dark. Examples: diorite (coarse), microdiorite (porphyritic) and volcanic andesite, named after the Andes.silicaplagioclasefeldsparamphibole
Acidic (felsic)silica more than 68% with sodium and potassium feldspars, mica, quartz (about 25%) and amphibole; light pink, crystallize below 800∘C. Examples: granite (coarse, used in construction and polished), microgranite (porphyritic), rhyolite (fine volcanic), obsidian (glassy) and pumice (frothy, light).silicasodiumpotassiumfeldspars

Classification by place of crystallization and texture

Comparison aspectMain ideaExampleKeywords
Plutonic rocks
  • slow cooling deep in the Earth lets ions gather at crystallization centres
  • giving coarse texture with a few large crystals visible to the eye (granite
  • diorite
  • gabbro
  • peridotite)
—slowcoolingdeepEarth
Intruded rocks
  • magma that rises but does not reach the surface cools between the surrounding rocks
  • slow cooling in depth gives large crystals and faster cooling nearer the surface gives small crystals. The texture is porphyritic (large crystals in a mass of small ones)
  • as in dolerite
  • microdiorite and microgranite
—magmarisesdoesreach
Extruded (volcanic) rocks
  • lava cools very fast on or near the surface
  • so crystals have no time to form: glassy texture (obsidian)
  • fine texture of microscopic crystals (rhyolite)
  • or frothy texture from gas bubbles (pumice). Basalt
  • andesite and komatiite have fine texture
—lavacoolsveryfast
Equivalent igneous rocks
  • have the same chemical and mineral composition but differ in place of formation
  • texture and grain size
  • granite (plutonic
  • coarse)
  • microgranite (intruded
  • porphyritic) and rhyolite (volcanic
  • microcrystalline)
samechemicalmineralcomposition

Shapes of igneous bodies in nature

Comparison aspectMain ideaKeywords
•Intruded (plutonic) bodiesIntrudedplutonicbodies
Batholith
  • the largest intruded bodies
  • extending hundreds of kilometres and several kilometres thick
largestintrudedbodiesextending
Domes
  • magma rises in a narrow slot and collects instead of spreading
  • a normal dome from viscous magma that lifts the layers above is a laccolith (causing an anticline)
  • while an inverted dome from fluid magma that bends the layers down is a lopolith (causing a syncline)
magmarisesnarrowslot
Dykesmagma intruded so that it cuts across the surrounding rockmagmaintrudedcutsacross
Sills
  • magma intruded parallel to the bedding planes
  • without cutting them
magmaintrudedparallelbedding
•Extruded (volcanic) bodiesExtrudedvolcanicbodies
Lava flowslava solidified on the surface in rope-like or pillow shapessolidifiedsurfaceropelike
Pyroclastics
  • (broken volcanic neck material): volcanic breccia with sharp-edged fragments around the volcano
  • and volcanic ash
  • very fine grains carried by wind for long distances
brokenvolcanicneckmaterial
Volcanic bombsoval massive pieces of lava that solidify near the surfaceovalmassivepieceslava
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 8 / 13
8 Sedimentary rocks

8 Sedimentary rocks

Formation

  1. Old igneous
  2. sedimentary or metamorphic rocks are broken up by weathering
  3. carried by transporting agents to depositional basins
  4. and deposited in parallel layers one over another.
  • They cover about three quarters of the crust in thin layers, but make only 5% of the crust by volume.
  • Most have economic value limestone, phosphate, coal, iron deposits and sandstone.
  • Muddy rocks are where oil, natural gas and kerogen form; porous rocks such as sandstone and limestone store oil, gas and groundwater.
  • Their types are few; mudstone, sandstone and limestone make about 90% of them.
Clastic (detrital) rocks→classified by the dominant size of the fragments, lithified by cementing material.
Rock Particle size Components Deposit
Conglomerate (rounded) and breccia (sharp-edged) More than 2 mm Pebbles, boulders Gravel
Sandstone 2 mm to 62 microns Quartz Sand
Mudstone (shale when laminated) 62 to 4 microns (silt); less than 4 microns (clay) Silt, clay Mud
Comparison aspectMain ideaKeywords
Chemical sedimentary rockssalts dissolved in water precipitate because of evaporation (higher concentration) or chemical reactionssaltsdissolvedwaterprecipitate
Calcareous rockslimestone and dolomitelimestonedolomite
Silicate rocksflintflint
Evaporites
  • gypsum (hydrated calcium sulphate)
  • anhydrite (calcium sulphate) and rock salt (halite
  • NaCl)
gypsumhydratedcalciumsulphate
Biogenic (biochemical) rocksfrom living organismslivingorganisms
Fossiliferous limestone
  • marine organisms build shells and skeletons of calcium carbonate taken from seawater
  • the remains accumulate after death
marineorganismsbuildshells
Phosphate rocks
  • fossilised remains of marine vertebrates that contain phosphate
  • plus phosphate minerals
fossilisedremainsmarinevertebrates
Comparison aspectMain ideaExampleKeywords
Coalplants are buried away from oxygen for a long time (
  • in swamps behind river deltas)
  • the tissues lose volatile parts and carbon becomes concentrated
plantsburiedawayoxygen
Oil and gashydrocarbons formed from the remains of marine micro-organisms buried with fine muddy sediments away from air—hydrocarbonsformedremainsmarine
•The source rocks are matured at 2 to 4 km depth at 70 to 100∘C; the hydrocarbons then migrate and gather in porous reservoir rocks (sand, sandstone, sometimes limestone).—sourcerocksmatureddepth
Oil shalea muddy rock rich in solid waxy kerogen of mainly plant origin, which turns into oil when heated to about 480∘C; it is kept as a reserve.—muddyrockrichsolid
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 9 / 13
9 Metamorphic rocks

9 Metamorphic rocks

Formation

Comparison aspectMain ideaKeywords
Metamorphism
  • is the change of a rock into a new state when the temperature and pressure increase
  • so that the rock re-equilibrates and recrystallizes
changerockstatetemperature
•
  • Any rock (igneous
  • sedimentary or metamorphic) may be metamorphosed
rockigneoussedimentarymetamorphic
Signs of metamorphism
  • new minerals form
  • the texture becomes more crystalline
  • and minerals arrange themselves perpendicular to the direction of the applied pressure
mineralsformtexturebecomes
Comparison aspectMain ideaKeywords
•
  • Formed by high temperature near a mass of magma (contact metamorphism)
  • the effect weakens with distance from the contact
  • and the crystals grow larger (massive granular texture)
Formedhightemperaturenear
Quartzitefrom sandstone (quartz) under very high temperaturesandstoneunderveryhigh
Marble
  • from limestone
  • the calcite crystals are cemented and compacted
  • so marble is hard and cohesive and is used as an ornamental stone
limestonecalcitecrystalscemented
Comparison aspectMain ideaKeywords
•
  • Temperature and pressure act together
  • crystals grow as flakes or sheets perpendicular to the pressure
  • forming foliation
Temperaturepressuretogethercrystals
Slatefrom shale under high pressure and relatively low temperature (below 200∘C); used in construction.shaleunderhighpressure
Schist(mica schist): mica crystals lie parallel in thin continuous sheetsmicacrystalsparallelthin
Gneiss
  • from granite under heat and pressure
  • the minerals form parallel
  • discontinuous bands
graniteunderheatpressure
Point of comparison Massive metamorphic Foliated metamorphic
Main cause High temperature (near magma) Temperature and pressure together
Texture Granular Sheets or bands (foliation)
Examples Quartzite, marble Slate, schist, gneiss
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 10 / 13
10 Weathering

10 Weathering

Definition and types

Comparison aspectMain ideaKeywords
Weathering
  • is the breakdown of rocks of the crust at the surface by mechanical and chemical factors
  • it is the first step of the rock cycle and the source of sediments
breakdownrockscrustsurface
Physical (mechanical) weatheringbreaks rock into pieces without changing its chemical compositionbreaksrockpieceswithout
Frost wedgingwater freezes in cracks and joints and the ice expandswaterfreezescracksjoints
Temperature changesrepeated heating and cooling cracks the rockrepeatedheatingcoolingcracks
Biological actionplant roots widen cracksplantrootswidencracks
Chemical weatheringchanges the minerals into new substanceschangesmineralssubstances
Oxidationiron-bearing minerals rustironbearingmineralsrust
Carbonation
  • rain containing dissolved carbon dioxide dissolves limestone
  • forming caves
raincontainingdissolveddioxide
Hydrolysisfeldspar in granite reacts with water and changes into the clay mineral kaolinitefeldspargranitereactswater
•Quartz resists chemical weathering because it is chemically stable silicon dioxideQuartzresistschemicalweathering
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 11 / 13
11 The rock cycle

11 The rock cycle

James Hutton and the cycle

  • The Scottish scientist James Hutton (1785) was the first to link the three types of rock with the action of the atmosphere and hydrosphere, which change rocks from one type to another in one cycle: the rock cycle.

Stages

Comparison aspectMain ideaKeywords
Weatheringbreaking up of the crust rocks by chemical and mechanical factorsbreakingcrustrockschemical
Transportation
  • the fragments are carried by natural agents and by gravity
  • exposing a new surface to weathering
fragmentscarriednaturalagents
Deposition
  • when the transporting agent loses its energy
  • it drops its load as sediments
transportingagentlosesenergy
Lithification
  • the sediments are compressed and cemented by a binding material
  • forming sedimentary rocks
sedimentscompressedcementedbinding
Metamorphism
  • heat
  • or heat and pressure
  • change rocks into new metamorphic rocks that suit the new conditions
heatpressurechangerocks
Melting
  • when the temperature reaches the melting point
  • the rocks melt and form magma
temperaturereachespointrocks
Cooling and crystallization
  • magma moves out
  • loses heat and crystallizes into igneous rocks
magmamoveslosesheat
•
  • Uplift then brings rocks back to the surface
  • and the cycle starts again
Upliftthenbringsrocks
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 12 / 13
Part 13

Part 13

  • 📖

🔍 In-Depth Explanations, Deductions & Multi-Book Insights:

  • DABOUR HUB ACADEMY • EGYPTIAN HIGH SCHOOL (THANAWEYA AMMA)
  • EXPLANATION Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering
  • Course Biology (Senior 3) | Chapter 7 – Geology, Earth Sciences and Ecology | Official Ministerial Syllabus 2026/2027
  • ―――――――――――――――――――――――――――――――――――――――――――――――――――――――

1. Academic Lesson Overview & Pedagogical Objectives

  1. James Hutton's rock cycle connecting Igneous
  2. Sedimentary
  3. and Metamorphic rocks
  4. mineral crystal systems
  5. physical and chemical weathering
  6. and sedimentary environments.

2. Hierarchy Classification Tree (Cognitive Concept Map)

  • Below is the hierarchical structural tree organizing the conceptual core of this lesson:

The Dynamic Rock Cycle & Minerals

├── 1. The Rock Cycle (James Hutton)

Comparison aspectMain ideaKeywords
│ ├── Igneous Rocks
  • Primary 'mother of rocks' from cooling magma (Plutonic granite
  • Volcanic basalt/obsidian)
Primarymothercoolingmagma
│ ├── Sedimentary Rocks
  • Weathering → Erosion → Transport → Deposition → Lithification (Sandstone
  • Limestone
  • Shale)
WeatheringErosionTransportDeposition
│ └── Metamorphic Rocks
  • Subjected to intense heat & pressure (Marble from Limestone
  • Quartzite from Sandstone)
Subjectedintenseheatpressure
•
  • ├── 2. Mineralogy & Crystallography: Silicates (most abundant)
  • Carbonates
  • Oxides
  • Sulfides
  • Halides
MineralogyCrystallographySilicatesmost
│ └── Crystal Systems
  • Isometric/Cubic (highest symmetry)
  • Tetragonal
  • Orthorhombic
  • Hexagonal
  • Monoclinic
IsometricCubichighestsymmetry
└── 3. Weathering Mechanisms
├── Physical WeatheringFrost wedging (ice expansion in joints), thermal fluctuation, biological roots
└── Chemical WeatheringOxidation (iron minerals), Carbonation (Limestone dissolving into caves), Hydrolysis (Feldspar into Kaolinite)

3. The Master Teacher's Blackboard & Exam Rules

Comparison aspectMain ideaKeywords
•
  • Extracted high-yield rules
  • golden equations
  • and trap warnings from top Egyptian teachers
Extractedhighyieldrules
• RULE 1Igneous rocks are the primary origin of all rocks ('Mother of rocks')Igneousrocksprimaryorigin
• RULE 2Chemical weathering of Feldspar in Granite under acidic rainwater produces Kaolinite clayChemicalweatheringFeldsparGranite
• RULE 3
  • Mohs Hardness Scale: 1 Talc
  • 2 Gypsum
  • 3 Calcite
  • 4 Fluorite
  • 5 Apatite
  • 6 Orthoclase
  • 7 Quartz
  • 8 Topaz
  • 9 Corundum
  • 10 Diamond
MohsHardnessScaleTalc
• TRAPQuartz does NOT undergo chemical weathering by carbonation because it is chemically stable silicon dioxide (SiO2)Quartzdoesundergochemical
Lesson 2: Rock Cycle, Minerals, Crystallography and Weathering · 13 / 13