min 2030 final exam: Part 2 - Lec 2 - Halides Carbonates Phosphates Nesosilicates

halides

• minerals where the anion is a halogen element

• Cl, F, Br, I

• larger anions than oxygen

• anions have -1 charge

only 3 are common:

• halite

• sylvite

• fluorite

halides- halite

• NaCl

• Face-centered cubic unit cell

• Isometric

• Perfect cleavage in 3 directions {100}, {010}, {001}

• Very soluble in water

• Tastes salty

• Typically forms cubic crystals when euhedral

• Sometimes “hoppered”

• Moh’s 2.5

• Generally colourless to white (Can even be blue, or coloured by impurities (yellow, grey, etc))

halides - sylvite

• KCl

• isomorphous with halite

  • same hardness, cleavage, crystal system and space group

• commonly occurs with halite

• can be colourless/white , grey, yellowish

• has a strong bitter salty taste

halite and sylvite

• form as evaporites- minerals precipitated from water as a result of evaporation

• can be found with other evaporite minerals - sulphates and borates

• can form from seawater or inland lakes

marine evaporites

• forms in isolated or semi isolated basins

• arid climates

• deposition of chemical sed rocks- carbonates, gypsum, halite

non-marine evaporites

• lakes or ponds

• arid climates

• deposition of chemical sed rocks- carbonates, gypsum, halite

diapirs

• A structure where ductile, buoyant material (like halite) pushes up through overlying sediments.

• Forms salt domes.

• Can act as non-porous traps for oil.

halides- fluorite

• CaF₂

• mohs 4

• isometric

• octahedral cleavage

• economically important

  • lowers melting point of metals and removes impurites

  • production of HF

• common colours- purple, green, blue, yellow

• commonly fluorescent in UV

carbonates

• (CO₃)^2- anionic group

• several are rock forming

• industrial minerals, ore minerals

• Calcite

• Aragonite

• Dolomite

• Magnesite

• Siderite

• Rhodochrosite

• Smithsonite

• Malachite

• Azurite

nitrates

• (NO₃)^- anionic group

• rare

borates

• (BO₃)^- anionic group

• found in evaporitic deposits

• ores of boron

• industrial minerals

• rare

carbonates- calcite group

trigonal carbonates with 2+ cation

• calcite

• magnesite

• siderite

• rhodochrosite

• smithsonite

carbonates- calcite group- calcite

• CaCO₃

• trigonal

• hardness 3

• reacts vigorously with HCl

• rhombohedral cleavage

• habits- massive, granular, rhombohedra, scalenohedra (dog tooth)

• wide range of colours- white, blue, grey, etc

• rock forming mineral

• accessory mineral in extremely wide range of rocks

calcite is a rock forming mineral in…

•Sedimentary carbonate rocks (limestone)

•Metamorphosed sedimentary carbonates (marble)

•Some hydrothermal veins (ore-bearing and not)

•Carbonatite magmatic rocks

•Skarn deposits

carbonatites

•Carbonate-rich plutonic and rarely volcanic

rocks

•Formed from low degree of partial melting of

upper mantle

•Calcite is abundant, may contain significant

dolomite and ankerite.

•Barite may be abundant in some deposits.

•Typically enriched in REE, Nb, Zr, Ti, P

(apatite).

• Important economic source of REE(rare earth elements) and Nb.

carbonates-calcite group- siderite

• very weak HCl reaction

• similar habits and cleavage to calcite

• large amounts in some hydrothermal ore depsits

• accessory mineral in shales, associated with coal seams

• commonly brown

carbonates- dolomite group

• trigonal carbonates with Ca²⁺

• dolomite

• ankerite

carbonites- dolomite group- dolomite

• similar properties to calcite

• commonly pinkish, colourless, grey, yellowish

• rock forming mineral in

  • •Sedimentary carbonate rocks (dolostone)

    •Metamorphosed sedimentary carbonates (dolomitic marble)

    •Carbonatite magmatic rocks (sometimes)

    •Skarn deposits (magnesianskarns only)

• accessory mineral in a wide range of rocks

• nearly impossible to discern from calcite without HCl test

• but form saddle shaped crystals

dolomite is a rock forming mineral in …

•Sedimentary carbonate rocks (dolostone)

•Metamorphosed sedimentary carbonates (dolomitic marble)

•Carbonatite magmatic rocks (sometimes)

•Skarn deposits (magnesianskarns only)

carbonates - aragonite group

orthorhombic carbonates with 2+ cation

• aragonite

• strontianite

• cerussite

carbonates- aragonite group- aragonite

• CaCO₃ - polymorph of calcite

• orthorhombic

• present in some modern sed carbonates

• found in high pressure metamorphic rocks where calcite is not stable

carbonates- azurite

• Cu₃(CO₃)₂(OH)₂

• bright blue

• light blue streak

carbonates- malachite

• Cu₂CO₃(OH)

• rich green

• light green streak

Cu carbonates

azurite and malachite

• can form in small quantities from the weathering of Cu-bearing minerals in the near surface (chalcopyrite), thin crusts in weathered rocks

• form in large quantities in the oxide zone of supergene copper deposits- as massive, radial, or botryoidal

• may occur together- especially in supergene deposits

sulphates

SO₄^2- anionic group

• Gypsum

• Anhydrite

• Barite

• Celestine

• Alunite

chromates and selenates

• Cr+O and Se+O anionic groups

• rare

sulphates- gypsum

• CaSO₄× 2H₂O

• monoclinic

• perfect cleavage on {010} and distinct on {100} (not basal)

• can have micaceous appearance

• mohs 2

• usually colourless, grey, yellowish

• habits: massive, platy or bladed, columnar aggregates, radial aggregates, “desert rose”

• occurs in larger quantities in evaporites

• commonly forms near surface in weathered sed rocks

  • low P-T hydrothermal deposits

sulphates- anhydrite

• CaSO₄ - anhydrous (no water)

• occurs in

  • evaporites with gypsum

  • diapirs, igneous rocks, metamorphosed evaporite rocks

how can you tell anhydrite and gypsum apart with the electron microprobe?

• there would be a weight % less than 100 for gypsum- EPMA cannot detect hydrogen

• anhydrite would be 100- there is no hydrogen

sulphates- barite

• BaSO₄

• occurs in accessory to rock forming amounts in some types of hydrothermal vein deposits, MVT Pb-Zn deposits, and carbonatites

• very common trace/ accessory mineral in sed carbonate rocks

• common in low-T hydrothermal veins

• associated with galena

• industrial uses and mined economically

• colours- whites, colourless, pinkish, yellowish, blue

• habits- massive, granular, radial, bladed aggregates, tabular, prismatic

• recognized by: habit, perfect cleavage, high density

sulphates- celestine

• SrSO₄ - ore of strontium

• similar settings to barite

• less common, but can occur in rock forming amounts in economic deposits (also in limestones)

• dense - SG 4

sulphates- alunite

• KAl₃(SO₄)₂(OH)₆

• yellow, colourless, greyish, reddish

• rare in the field

• occurs in veins and zones of alteration in K-rich volcanic rocks

phosphates

(PO₄)^3- anionic groups

• some are very common as accessory minerals in a wide range of environments

• present in larger, even rock forming amounts in some unusual environments

• Apatite

• Monazite

• Turquoise

• Pyromorphite

• Vivianite

phosphates- apatite

• three Ca phosphates which form a solid solution series based on different -1 charged anions

• fluorapatite- most common

• hydroxylapatite- very uncommon (bones)

• chlorapatite- very rare

phosphates- apatite

• Ca₅(PO₄)₃F (fluora-)

• prismatic, euhedral or subhedral crystals

• hexagonal

• poor cleavage

• mohs 5

• typically green-blue, grey, colourless, reddish brown

• very common trace/accessory mineral

• rarely occurs in rock forming amounts in coarse grained carbonate intrusive rocks

• mined for use in fertilizer

• useful for fission-track dating

fission track dating

•Uranium radioactive decay ejects

particles which cause ‘tracks’ of

damage in a mineral grain

•They can be used for

thermochronology–determining

the age at which a rock cooled

below the annealing temperature

of apatite or other minerals

phosphates- monazite

• three monazite species which forma solid solution based on the dominant rare earth element

• (REE)PO₄

• Ce- most common

• Nd- neodymium

• La- Lanthanum

• common trace mineral, rare accessory mineral (except in REE-rich deposits)

• can be age dated using the U-Pb system

• ore mineral of REE and Th

• most abundant in carbonatites, alkaline plutonic rocks, and some type of granitic pegmatite

monazite thin section

• olive-yellow green

• high relief

• high birefringence

• biaxial- monoclinic

• commonly has radio halos

arsenates- annabergite

• Ni₃(AsO₄)₂ × 8H₂O

• green, low P-T alteration of Ni-As bearing ores

• in tailings cobalt, Ontario 5 element veins

arsenates- erythrite

• Co₃(AsO₄)₂ × 8H₂O

• “cobalt bloom”

• bright pink, low P-T, near-surface alteration of Co-As-bearing ores

• in tailings at cobalt, ontario 5 elements veins

silicates

• silica tetrahedron forms the basis of this mineral class

• (SiO₄)^4-

• most abundant mineral group in earths crust

• divided into subclasses based on the structural arrangement of silica tetrahedra

• composition of most rocks

nesosilicates

single isolated silica tetrahedra (SiO₄^4-)

• Olivine

• Garnet

• Zircon

• Kyanite

• Andalusite

• Sillimanite

• Topaz

• Staurolite

sorosilicates

double silica tetrahedra joined at one vertex (Si₂O₇^6-)

• Epidote

• Zoisite

• Lawsonite

• Vesuvianite (Idocrase)

• Hemimorphite

• Allanite

cyclosilicates

Silica tetrahedra arranged into rings. Number of tetrahedra is variable in different mineral species. (4, 6 and 8)

• Beryl

• Tourmaline

• Cordierite

• Benitoite

• Dioptase

inosilicates

silica tetrahedra form single or double chains

Single-chain (pyroxenes):

• Augite

• Diopside

• Enstatite

• Hedenbergite

Double-chain (amphiboles):

• Hornblende

• Actinolite

• Tremolite

• Glaucophane

phyllosilicates

silica tetrahedra form sheets

• Muscovite

• Biotite

• Chlorite

• Kaolinite

• Illite

• Smectite (Montmorillonite)

• Serpentine

• Talc

tectosilicates

silica tetrahedra form 3 dimensional framework structures

• Quartz

• Orthoclase (K-feldspar)

• Plagioclase feldspar

• Microcline

• Albite

• Nepheline

• Leucite

• Sodalite

nesosilicates- olivine

group: M₂SiO₄

• M= Ca, Fe, Mn, Ni, Mg

• forsterite-fayalite solid solution series most common

• orthorhombic

• mohs 7

• no cleavage, conchoidal fracture

• typically yellow-green, green, brown

• common in ultramafic and mafic rocks, often rock forming amounts

• extremely abundant in the mantle

• can occur in Mg-rich marbles metamorphosed at high grade

• does not occur with quartz!

• weathers very easily at the surface

nickel laterites

Ni ore deposits formed from the intense weathering of Ni-bearing olivine in ultramafic rocks

nesosilicates- garnet group

generalized formula: X₃Z₂(SiO₄)₃

• isometric -equant, dodecahedral

• mohs 6.5-7.5

• no cleavage

• typically adamantine or glassy

• wide range of colours- depends on concentration of end-members, Cr has strong green colouring effect

The most common end-members are:

• Grossular: Ca₃Al₂(SiO₄)₃

• Almandine: Fe²⁺₃Al₂(SiO₄)₃

• Pyrope: Mg₃Al₂(SiO₄)₃

• Spessartine: Mn²⁺₃Al₂(SiO₄)₃

• Andradite: Ca₃Fe³⁺₂(SiO₄)₃

• Uvarovite: Ca₃Cr₂(SiO₄)₃ (rare, only in Cr-rich rocks)

spessartine

orange to red garnet

• occur in granites and granite pegmatites

pyrope, almandine, andradite

red to reddish brown garnet

grossular

colourless, pinkish to orange garnet

common rock types that garnets occur in

• Grossular- skarns and contact-metamorphosed marbles/limestones, rodingites

• Almandine- Metamorphic rocks (gneiss, schist), granites

• Pyrope- Kimberlites (xenocrysts), Mg-rich high pressure metamorphic rocks

• Spessartine- Granites and granitic pegmatites

• Andradite- skarn deposits, serpentinites

• Urarovite- altered chromite deposits