Dr. Mihelcic Honors Chemistry1 Chemical Kinetics Rates and Mechanisms of Chemical Reactions.
GeGemstones Colour Chemistry1mstones Colour Chemistry1
2
CHEMICAL C OMPOSIT ION OF GEMS TONES BY NC ND © COMPOUND INTEREST 2014 - WWW.COMPOUNDCHEM.COM Shared under a Creative Commons Attribution-NC-ND licence. For more information & references, see www.compoundchem.com/2014/06/28/gemstones C ALEXANDRITE Al 2 BeO 4 Colour caused by chromium ions replacing aluminium in some sites. Colour varies in different light. Hardness: 8.5 AMETHYST SiO 2 Their colour is caused by iron 3+ ions replacing silicon in some locations in the structure. Hardness: 7.0 AQUAMARINE Be 3 Al 2 (SiO 3 ) 6 Colour caused by iron 2+/3+ ions replacing aluminium ions in some locations in the structure. Hardness: 7.5-8.0 DIAMOND C Colourless; can be faintly coloured by the trapping of nitrogen atoms in the crystal. Hardness: 10 GARNET Mg 3 Al 2 (SiO 4 ) 3 Colour caused by iron 2+ ions replacing magnesium ions in some locations in the structure. Hardness: 6.5-7.5 EMERALD Be 3 Al 2 (SiO 3 ) 6 Colour caused by chromium ions replacing aluminium in some locations in the structure. Hardness: 7.5-8.0 OPAL SiO 2 .nH 2 O Many colours which are caused by interference & diffraction of light passing through the structure. Hardness: 5.5-6.0 PEARL CaCO 3 Produced in the soft tissue of shelled molluscs. The thinner the layers of the pearl, the finer the lustre. Hardness: 2.5-4.5 PERIDOT Mg 2 SiO 4 Colour caused by iron 2+ ions replacing magnesium ions in some locations in the structure. Hardness: 6.5-7.0 RUBY Al 2 O 3 Colour caused by chromium ions replacing aluminium ions in some locations in the structure. Hardness: 9.0 SAPPHIRE Al 2 O 3 Colour caused by titanium and iron ions replacing aluminium ions in some locations in the structure. Hardness: 9.0 T OP A Z Al 2 SiO 4 (F,OH) 2 Pure topaz gems are colourless & transparent, but tinted by impurities they can have a variety of colours. Hardness: 8.0 T OU R M A L IN E Na 3 Li 3 Al 6 (B O 3 ) 3 (SiO 3 ) 6 F 4 Colour caused by manganese ions replacing lithium and aluminium ions in some sites. Hardness: 7.0-7.5 T UR QU IO S E Al 6 (PO 4 ) 4 (OH) 8 .4H 2 O Colour caused by the presence of copper ions coordinated to the hydroxide ions and water. Hardness: 5.0-6.0 ZIRCON ZrSiO 4 A range of possible colours that depend on the impurities present. Colourless specimens are popular diamond substitutes. Hardness: 7.5 SPINEL MgAl 2 O 4 A variety of colours are possible, caused by impurities such as iron, chromium and nickel. Hardness: 7.5-8.0 THE COLOURS OF GEMSTONES ARE AFFECTED BY DIFFERENCES IN CHEMICAL AND ATOMIC STRUCTURE, LEADING TO THE ABSORPTION OF DIFFERENT WA VELENGTHS OF LIGHT. THEIR HARDNESS IS MEASURED ON THE MOHS SCALE, WHICH RUNS FROM 0-10.
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CHEMICAL COMPOSITION OF GEMSTONES
BY NC ND
© COMPOUND INTEREST 2014 - WWW.COMPOUNDCHEM.COMShared under a Creative Commons Attribution-NC-ND licence.For more information & references, see www.compoundchem.com/2014/06/28/gemstones
C
ALEXANDRITEAl
2BeO
4
Colour caused by chromium ions
replacing aluminium in some sites.
Colour varies in different light.
Hardness: 8.5
AMETHYSTSiO
2
Their colour is caused by iron 3+
ions replacing silicon in some
locations in the structure.
Hardness: 7.0
AQUAMARINEBe
3Al
2(SiO
3)
6
Colour caused by iron 2+/3+ ions
replacing aluminium ions in some
locations in the structure.
Hardness: 7.5-8.0
DIAMONDC
Colourless; can be faintly coloured
by the trapping of nitrogen atoms
in the crystal.
Hardness: 10
GARNETMg
3Al
2(SiO
4)3
Colour caused by iron 2+ ions
replacing magnesium ions in
some locations in the structure.
Hardness: 6.5-7.5
EMERALDBe
3Al
2(SiO
3)
6
Colour caused by chromium ions
replacing aluminium in some
locations in the structure.
Hardness: 7.5-8.0
OPALSiO
2.nH
2O
Many colours which are caused by
interference & diffraction of light
passing through the structure.
Hardness: 5.5-6.0
PEARLCaCO
3
Produced in the soft tissue of shelled
molluscs. The thinner the layers of
the pearl, the finer the lustre.
Hardness: 2.5-4.5
PERIDOTMg
2SiO
4
Colour caused by iron 2+ ions
replacing magnesium ions in
some locations in the structure.
Hardness: 6.5-7.0
RUBYAl
2O
3
Colour caused by chromium ions
replacing aluminium ions in some
locations in the structure.
Hardness: 9.0
SAPPHIREAl
2O
3
Colour caused by titanium and
iron ions replacing aluminium ions
in some locations in the structure.
Hardness: 9.0
TOPAZAl
2SiO
4(F,OH)
2
Pure topaz gems are colourless &transparent, but tinted by impurities
they can have a variety of colours.
Hardness: 8.0
TOURMALINENa
3Li
3Al
6(BO
3)3(SiO
3)
6F
4
Colour caused by manganese ionsreplacing lithium and aluminium
ions in some sites.
Hardness: 7.0-7.5
TURQUIOSEAl
6(PO
4)
4(OH)
8.4H
2O
Colour caused by the presenceof copper ions coordinated to the
hydroxide ions and water.
Hardness: 5.0-6.0
ZIRCONZrSiO
4
A range of possible colours thatdepend on the impurities present.Colourless specimens are popular
diamond substitutes.
Hardness: 7.5
SPINELMgAl
2O
4
A variety of colours are possible,
caused by impurities such as iron,
chromium and nickel.
Hardness: 7.5-8.0
THE COLOURS OF GEMSTONES ARE AFFECTED BY DIFFERENCES IN CHEMICAL AND ATOMIC STRUCTURE, LEADING TO THE ABSORPTION OFDIFFERENT WAVELENGTHS OF LIGHT. THEIR HARDNESS IS MEASURED ON THE MOHS SCALE, WHICH RUNS FROM 0-10.
