Known Minerals

Recognition and Description of Minerals - Knowns ISOTROPIC MINERALS Halite NaCl Sylvite KCl

Fluorite CaF2 Periclase MgO 2+ 3+ Garnet (Ca,Mg,Fe ,Mn)3Al,Fe ,Cr)2(SiO4)3

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Recognition and Description of Minerals - Knowns UNIAXIAL MINERALS

Quartz SiO2

Calcite CaCO3

Nepheline NaAlSiO4

Apatite Ca5(PO4)3(F,Cl,OH)

Zircon ZrSiO4 Tourmaline Boro-Silicate

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Recognition and Description of Minerals - Knowns BIAXIAL MINERALS

Olivine (Mg,Fe)2SiO4

Orthopyroxene (Mg,Fe)2Si2O6

Clinopyroxene (Ca,Mg,Fe,Al)2Si2O6

Hornblende Ca2(Mg,Fe,Al)5Si8O22(OH)2

Tremolite Ca2Mg5Si8O22(OH)2

Actinolite Ca2Fe5Si8O22(OH)2

Biotite K2(Mg,Fe)3AlSi3O10(OH,F)2

Muscovite KAl2(AlSi3O10)(OH)2

Chlorite (Mg,Al,Fe)3(Si,Al)4O10(OH)2*(Mg,Al,Fe)3(OH)6

Plagioclase (Na,Ca)Al(Al,Si)Si2O8

Alkali Feldspar KAlSi3O8

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1 Features Useful in the Identification of a Mineral • Shape of grains • Degree of crystallinity • Cleavage • Twinning • Alteration • Associations

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Shape of grains • Acicular needle-like grains (actinolite, tremolite) • Bladed elongate, slender (hornblende) • Columnar elongate with equidimensional cross sections (quartz, pyroxenes) • Equant equidimensional grains (quartz, olivine) • Fibrous grains form long slender fibers (asbestos, sillimanite) • Lathlike flat elongate grains (plagioclase) • Prismatic crystal faces defined by prism (apatite) • Tabular book shape (plagioclase)

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Bladed Grains

Hornblende

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2 Equant Grains

qtz

Fibrous Grains

bio bio

sill sill

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Lath-like Grains

pl pl

cpx cpx

pl pl

pl pl cpx cpx

3 Prismatic Grains

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Degree of Crystallinity

• ______• grains have well formed crystal faces

• ______• poorly formed and/or irregular crystal faces

• ______• no regular crystal faces

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Cleavage • In grain mounts, ______on grains indicate the presence of ______• In thin section, cleavage is difficult to recognize in minerals with a low relief, under normal circumstances • By closing the aperture diaphragm cleavage is more readily seen

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4 Cleavage • Grains at the edge of the section may exhibit cleavage more so than grains in the centre • ______between cleavages is useful for identifying the broad mineral group – Pyroxene - 2 at 90° – Amphibole – 2 at 56°/124° – Alkali Feldspar - 2 at 90° – Plagioclase – 2 cleavages at 94°

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Cleavage

bio

hbl

Twinning •Presence and nature of the twins may be ______•A variety of twin laws may be observed in thin section

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5 Simple Twin

Two segments of one grain go extinct at different times on rotating the stage

0.5 mm

cpx

0.5 mm

Contact Joined by a smooth twin plane separating the segments Twins Carlsbad-albite Twin Plane

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Penetration Twin

Joined by an irregular contact

0.5 mm

staur

0.5 mm © G.C. Finn, 2005 ERSC 2P22 – Brock University Greg Finn

6 Polysynthetic Consists of numerous twin segments joined on parallel twin planes Twin

Albite Twin pl Plane

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Alteration •The type of alteration product observed within an individual grain may be used to identify that grain •e.g. – iddingsite alteration of olivine – sericite alteration of plagioclase – clay minerals from alkali feldspars

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Olivine altering to Serpentine

ol ol

ser ser ol ol

ol ol

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7 Plag altering to Sericite

pl pl

sericite sericite

pl pl

From: http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/ig_minerals.htm

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Associations • Knowing the common mineral associations in a variety of rock types may aid in making an "educated guess" as to the identity of an unknown mineral • Knowing the mineral association for a given rock may aid in the identification of a specific mineral which might otherwise have been overlooked • Appendix C of Nesse lists the common igneous, metamorphic and sedimentary rocks and expected mineralogy in each

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Mineralogy of Common Igneous Rocks

Rock Type Major (>10%) Minor (<10%) Accessory

Allanite, apatite, epidote, Felsic Quartz, Muscovite, biotite, magnetite, ilmenite, hematite, (granite, rhyolite, hornblende fluorite, garnet, monazite, granodiorite, etc.) K-feldspar, sillimanite, tourmaline, zircon plagioclase (Ab-ol)

Allanite, apatite, epidote, Intermediate Plagioclase (And), Quartz, biotite, magnetite, ilmenite, hematite, (diorite, tonalite, dacite, hornblende muscovite, opx, zircon andesite) cpx

Apatite, chromite, magnetite, Mafic Plagioclase (Lab - Biotite, ilmenite, hematite, spinel (basalt, gabbro, norite, By), cpx, opx, hornblende peridotite) olivine

Apatite, epidote, magnetite, Si-deficient K-feldspar, Biotite, muscovite, ilmenite, hematite, melilite, Rare- (syenite, phonolite) plagioclase (Ab- Na-amphibole, Earth minerals And), nepheline, Na-pyroxene leucite, sodalite

From: Nesse 2004, Appendix C.1

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8 Mineralogy of Common Sedimentary Rocks

Clastic Carbonate Evaporite

Quartz Calcite Anhydrite K-feldspar Dolomite Calcite Plagioclase Clay Chalcedony Clay Glauconite Dolomite Chalcedony Clastic material Gypsum Calcite Skeletal remains Halite Muscovite Sulfur Biotite Sylvite Glauconite Clastic material Magnetite Ilmenite Hematitie Zeolites PLUS MANY MORE

From: Nesse 2004, Appendix C.2

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Mineralogy of Common Metamorphic Rocks Rock Type Common Accessory Quartz, plagioclase, muscovite, Apatite, epidote, graphite, hematite, ilmenite, magnetite, tourmailine Pelite (shale) chlorite, biotite, garnet, chloritoid, andalusite, kyanite, sillimanite, staurolite, K-feldspar Plagioclase, amphibole, cpx, Apatite, hematite, ilmenite, magnetite, spinel, Mafic (basalt) zircon biotite, quartz, titanite, calcite, chlorite, epidote, garnet, Calcite, dolomite, epidote, Corundum, graphite, hematite, ilmenite, magnetite, titanite Carbonate (limestone) garnet, cpx, amphibole, biotite, olivine, quartz, aragonite, wollastonite, talc, scapolite, periclase, brucite Quartz, K-feldspar, plagioclase, Allanite, apatite, epidote, garnet, hematite, ilmenite, magnetits zircon Granitic Gneiss (felsic, biotite, cordierite, hornblende, sediments) opx Quartz, plagioclase, epidote, Apatite, hematite, ilmenite, magnetite, Metagraywacke (high and prehnite, ziorcon low pressure rocks) pumpellyite, lawsonite, chlorite, biotite, stilpnomelane, muscovite, omphacite, Na- amphibole, calcite, aragonite, garnet, serpentine, titanite, zircon

From: Nesse 2004, Appendix C.3 ERSC 2P22 – Brock University Greg Finn