Mineralogy

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Mineralogy
Minerals and crystals
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Worlds largest crystals A cave in the Naica
Lead Zinc mine, Mexico
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Miners in Cueva de los Crystals the mineral
gypsum
Crystals of a variety of gypsum (CaSO4.2H2O)
precipitated from hot water at 60 degrees celsius
in a limestone cave in the Naica mine
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Minerals
Tourmaline on Feldspar
Beryl (Be3Al2(SiO3)6
Emerald
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Crystal Shapes
Quartz (SiO2)
Diamond (C)
Halite (NaCl)
Calcite (CaCO3)
Stibnite (Sb2S3)
Garnet (Fe3Al2Si3O12)
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Pyrite (FeS2) crystals
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Feldspars two of the most important
rock-forming minerals
Plagioclase
Albite NaAlSi3O8
Anorthite CaAl2Si2O8
K-feldspar
Sanidine
Orthoclase
Microcline
KAlSi3O8
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Colours and forms of quartz
Citrine
Amethyst
Milky quartz
Rose quartz
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Quartz crystals displaying prism and pyramid faces
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Quartz Crystal
Pyramid
Faces display consistent angular relationships
Angles measured with a goniometer
Prism
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Crystals have ordered arrangements of atoms
Order
Disorder
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X-ray diffraction
X-ray beam splits into numerous smaller beams.
Interference of waves of different beams produces
a diffraction pattern on a screen or film. The
pattern indicates the spacing and arrangement of
atoms.
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Atomic structure of galena (PbS)
Surface of galena (PbS) imaged With an atomic
force microscope
Sulphur
Lead
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The atomic structure of halite (NaCl)
Ionic bonding
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Ionic bonding transfer of electrons
Anion -
Cation
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Relative sizes of ions
Ion co-ordination
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The atomic structure of diamond
Covalent bonding
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The source of Diamonds
The Big Hole at Kimberly, South Africa
Kimberlite containing diamond
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Cutting diamonds
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Covalent bonding sharing of electrons
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Atomic structure of graphite
Covalent bonding within sheet
Van der Waals bonding between sheets
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Ice Crystals
Hydrogen bonding
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The silicon tetrahedron
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Silicate Structures
Inosilicate
Inosilicate
Nesosilicate
(Single chain)
(Double chain)
SiO44 -
Si4O116 -
SiO32-
Sheet silicate
Framework silicate
Si4O104 -
SiO2
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Nesosilicate
(Fe,Mg)2SiO4
Olivine
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Inosilicate (Single Chain)
Diopside
Pyroxene
CaMgSi2O6
Hypersthene
(Fe,Mg)SiO3
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Inosilicate (Double Chain)
Amphibole
Tremolite Ca2Mg5Si8O22(OH)2
Riebeckite Na2Fe5Si8O22(OH)2
Tigers Eye
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Asbestos
Chrysotile (Mg3Si2O5(OH)4
Uses and risks
(Insulation, heat, fire resistance)
Serpentine (Mg3Si2O5(OH)4
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Sheet Silicate
Biotite KAl(Fe,Mg)3Si3O10(OH)2
Muscovite KAl3Si3O10(OH)2
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Framework Silicate
Quartz SiO2
Albite NaAlSi3O8
Plagioclase
Anorthite CaAl2Si2O8
Amethyst SiO2
K-feldspar KAlSi3O8
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Relationship of Quartz structure to Feldspar
Structure
Imagine four SiO2 molecules 4 x SiO2 Si4O8
Substitute Al3 for Si4 in one of these molecules
Add Na or K to supply missing charge
NaAlSi3O8 or KAlSi3O8
Albite K-Feldspar
Add Ca2 to supply missing charge CaAl2Si2O8
Anorthite