GEOLOGY 200A - Mineralogy Test
Give the formula, [e.g. (Mg,Fe)2Si2O6, CaAl2Si2O8/NaAlSi3O8], the name and formula, where applicable, of the end-members of any solid solution series, e.g. forsterite Mg2SiO4-fayalite Fe2SiO4, and those features such as colour, luster, cleavage, fracture, hardness, density, as well as other characteristics such as reaction to acid, magnetism, etc, that might allow you to identify the following minerals in coarse grained rocks :
Plagioclase
Formula End member 1 Anorthite CaAl2Si2O8 End
member 2 Albite NaAlSi3O8
Colour white lustre vitreous cleavage 2, one perfect
hardness 6 density 2.7
Other : - albite twinning; striations.
Orthoclase
Formula KAlSi3O8
Colour pink lustre vitreous cleavage two perfect
hardness 6 density 2.6
Other : - commonly twinned (bonus)
Clinopyroxene
Formula - Ca(Mg,Fe)Si2O6 End member 1 Diopside CaMgSi2O6
End member 2 Hedenbergite CaFeSi2O6
Colour black - green lustre vitreous cleavage 2 at
right angles hardness 6 density 3.2
Other : - prismatic square cross sections (bonus)
Orthopyroxene
Formula - (Mg,Fe)2Si2O6 End member 1 Enstatite Mg2Si2O6
End member 2 Ferrosilite Fe2Si2O6
Colour Greenish yellow to bronze lustre vitreous to pearly cleavage
two at right angles hardness 6 density 3.2
Other : - commonly occurs with olivine and chromite (bonus)
Olivine
Formula - (Mg,Fe)2SiO4 - End member 1 Forsterite Mg2SiO4
End member 2 Fayalite Fe2SiO4
Colour green lustre vitreous cleavage none
hardness 6.5 density 3.5
Other : - commonly granular
Ilmenite
Formula FeTiO3
Colour black lustre metallic cleavage none
hardness 6 density 4-5
Other : - may be slightly magnetic
Apatite
Formula Ca5(PO4)3.(OH,F,Cl)
Colour light green lustre vitreous cleavage poor
hardness 5 density 3.2
Other : - hexagonal prismatic
Magnetite
Formula FeO.Fe2O3
Colour black lustre metallic cleavage none
hardness 6 density 5
Other : - magnetic, octohedrons
Quartz
Formula SiO2
Colour clear lustre vitreous cleavage none
hardness 7 density 2,7
Other : - hexagonal; conchoidal
fracture
Amphibole
Formula - Ca2(Mg,Fe)5Si 8 O22(OH)2 End member 1 Tremolite
Ca2Mg5Si 8 O22(OH)2 End member 2 Actinolite Ca2Fe5Si 8 O22(OH)2
Colour black to green lustre vitreous cleavage 2 at 120
degrees hardness 6 density 3-3.5
Other : - prismatic, acicular
Glaucophane
Formula Na2Mg3Al2Si8O22(OH)2
Colour Lavender blue lustre vitreous cleavage 1 good
hardness 6 density 3.3
Other : - acicular
Epidote
Formula Ca2Al3Si3O12(OH)
Colour pistachio green lustre vitreous cleavage 1
perfect hardness 6 density 3.4
Other : -
Garnet
Formula Ca(Mg,Fe)3Al2Si3O12 End member 1) Grossularite,
Ca3; End member 2) Pyrope, Mg3; End member 3) Almandine, Fe3;
(under conditions of low temperature metamorphism there also exists
end member 4 Mn3, Spessartine)
Colour red, green white lustre vitreous cleavage none
hardness 7 density 3.5-4
Other : - - dodecahedral form
Mica
Formula - End member 1 Muscovite KAl3Si3O10(OH)2
End member 2 Biotite KAl(Mg,Fe)3Si3O10(OH)2
Colour white to brown lustre transparent cleavage flaky
hardness 2.5 density 2.8
Other : -
Pyrite
Formula FeS2
Colour yellow lustre metallic cleavage poor
hardness 6-6.5 density 5
Other : - reacts with acid
Chlorite
Formula (Mg,Fe)2Al2SiO5(OH)4 - (Mg,Fe)3Al2Si3O10(OH)2
Colour green lustre vitreous cleavage flaky
hardness 2 density 3
Other : -
Kyanite
Formula Al2SiO5
Colour blue white lustre vitreous cleavage prominent
hardness 6 density 3.5
Other : - cross fracture
cleavage
Corundum
Formula Al2O3
Colour lustre vitreous, gem cleavage
none hardness 9 density 4
Other : - hexagonal barrel shaped
Calcite
Formula CaCO3
Colour transparent lustre vitreous cleavage 3 perfect
hardness 3 density 3
Other : - reacts with acid
Kaolinite
Formula Al2Si2O5(OH)4
Colour white lustre earthy cleavage perfect
hardness 2 density 2.5
Other : -
Serpentine
Formula Mg3Si2O5(OH)4
Colour green white lustre pearly cleavage perfect
hardness 2.5 density 2.5
Other : -
Talc
Formula Mg3Si4O10(OH)2
Colour white lustre greasy cleavage perfect
hardness 1 density 2.6
Other : -