EES201

minerals made of a single element in uncombined form — not alloyed, not bonded to anything else.

Native elements

sulphur is

strong reudcing agent

mineral formed in reducing environment and is very insoluble in water

Sulphide

mineral formed in oxidizing environmnet and is soluble in water

Sulphate

has a very high affinity for bonding with heavy metal cations

Sulphur

An important manganese ore, typically found in metamorphic rocks and manganese-rich zones. MnO2

Pyrolusite

An excellent electrical/thermal insulator with an extremely high melting point Because it can tolerate very high heat without breaking down, it's used to line industrial furnace chimneys in steel factories. It's rigid and brittle, but once installed, lasts a long time under sustained high heat. MgO

periclase

a more complex halide containing copper, chlorine, and hydroxide together. It's related to the green patina seen on weathered copper and bronze objects — sometimes informally called "bronze disease."

atacamite

a copper carbonate mineral

malachite

Important primarily as a source of fertilizers

nitrates

most abundant mineral

feldspar

weathered feldspar and mica

clay

high energy water

coarse grain deposition

low enegry water

fine particle deposition

these form the oceaic crust, has higher density hence sit low, rich in dense silicates

Basalt and gabbro

these minerals forms the continental crust, has low density hence rises up, and is rich in quartz and alkali feldspar

granite

Basalt, gabbro and granite

igneous rocks

Dominated by quartz grains some feldspar and clay is mixed in when cemented together, but individual grains are mostly quartz. Forms in higher-energy, near-water-body conditions, giving coarser, more porous grains.

Sandstone

Dominated by clay minerals. Forms in low-energy, deep-ocean conditions far from strong water movement — hence much finer grain size than sandstone. When ocean floor gets uplifted (the Himalayas were used as the example again), you find shale/clay deposits marking what used to be a seabed.

shale

deposition is not primarily controlled by water energy — it's controlled by pH and depth You need the right pH conditions and an existing carbonate source material for more carbonate to deposit — similar logic to carbonate buildup in caves.

carbonate rocks

Si--O bond length

162pm

ratio of Nesosilicates

1:4

Examples of Nesosilicates

Olivine, Garnet and zircon

ratio of Sorosilicate

2:7

Example sorosilicates

epidote and zoisite

ratio of cyclosilicates

1:3

example of cyclosilicates

beryl and tourmaline

ratio of single chain inosilicates

1:3

examples of single chain inosilicates

pyroxene, including enstatite,augite

ratio of double chain inosilicates

4:11

example of double chain inosilicates

amphibole: hornblende and tremolite

ratio of phyllosilicates

2:5

examples of phyllosilicates

mica

ratio of tectosillicates

1:2

examples of tectosilicates

quartz, feldspar, zeolites

which subclass of silicates has a structure similar to C60 fullerene

tectosilicates

flat, blade-like crystals.

Bladed

thin, needle-like crystals

Acicular

thread-like, classically seen in asbestos; compared to the fibres you'd see inside a broken piece of wood.

Fibrous

Smooth, curved break — like broken glass

Conchoidal

ex of conchoidal

quartz and other amorphous, non cleaving minerals

Thin, thread-like splinters

Fibrous / splintery

example of fibrous

asbestos type mineral

Sharp, jagged edges — random each time, but always sharp

Hackly

Unpredictable break pattern, not sharp

Irregular / uneven

One nucleus forms from the melt and simply continues growing larger over time — often showing internal zonation (layered growth bands) as conditions shift.

Single crystal growth

Instead of one crystal growing large, many small crystals form together as a cluster. This is described as more energetically favourable — growing many small crystals costs less energy than growing one large one, which is why aggregates are actually the more common outcome unless conditions specifically favour large single crystals (e.g. a melt that's cooling slowly and not being disturbed/moved much).

Aggregate formation

A hybrid mode: an aggregate forms first, then a single nucleus forms within that aggregate, and the surrounding aggregate progressively fuses into that single growing crystal — producing an emergent larger crystal out of what started as a cluster.

Nucleation-within-aggregate

disrupting an existing crystal's formation conditions, then letting it re-form under new conditions

recrystallization

discourages crystal formation, since atoms don't stay together long enough to bond.

Thermal vibration

________ between atoms encourage crystal formation by pulling atoms together despite the vibration

Attractive forces

When a melt cools extremely fast, it doesn't get time to form ordered crystals at all — it freezes into a disordered, glassy (amorphous) solid instead

full sequence — glass forming, then later melting and recrystallizing

Cold crystallization

negative ΔG

products are more stable than the starting materials

the chemical conditions present throughout that entire growth period get physically recorded, layer by layer, inside the crystal — this recorded layering is called

zoning

conditions stayed stable over a long period.

Thick zones

conditions changed frequently.

Thin zones

the first small cluster of atoms that comes together as a melt cools

nucleus

Atoms spontaneously cluster together on their own, with no pre-existing surface or seed to start from — purely from random atomic collisions finding a stable arrangement by chance.

Homogeneous nucleation

New mineral growth uses a pre-existing surface or structure as a starting seed. This is especially common in metamorphic settings, where solid and melt phases coexist and an already-solid mineral surface can act as the nucleus for a new mineral.

Heterogeneous nucleation

far below the mineral's melting point the melt has been cooled

Undercooling

cooling only slightly below the melting point, slowly

Small undercooling

cooling far below the melting point, quickly.

Large undercooling

large undercooling

many small crystals

small undercooling

few large crystals

small undercooling(critical radius)

large

large undercooling(critical radius)

small

in mantle level we see

small undercooling

near surface we see

large undercooling

________ forms a distinctive, perfectly-shaped crystal — a dodecahedron

garnet

Atomic-level — a single missing, misplaced, or substituted atom/ion

defect

Crystal-level (macroscopic pattern of many atomic bonds)

cleavage plane

a lattice defect where part of the structure is offset/sheared, similar in concept to a geological fault — creates a permanent step or edge on the crystal surface.

screw dislocation

0-dimensional (a single atomic site) imperfections in an otherwise perfectly repeating lattice.

Point defects

one cation and one anion missing together from their lattice sites, keeping the crystal electrically neutral overall.

Schottky defect

Schottky defect

density: decreases

An ion leaves its normal lattice position and lodges itself in a nearby interstitial site (a gap between normal lattice positions) instead — so the ion isn't missing from the crystal overall, it's just displaced/out of place.

Frenkel defect

Frenkel defect

density: stays constant

A foreign ion of similar size to the original occupies a lattice site in its place

Substitutional (impurity) defect

Substitutional (impurity) defect

density: depends — whether density rises or falls depends specifically on whether the substituting ion is heavier or lighter than the one it replaced

a physical property varying depending on which crystallographic direction you measure it in

anisotropy