B2S7: Colour Flashcards
What is the symbol for Titanium? What colour does it produce?
Ti
Blue
What is the symbol for Vanadium? What colour does it produce?
V
Green, pink
What is the symbol for Chromium? What colour does it produce?
Cr
Red, green
What is the symbol for Manganese? What colour does it produce?
Mn
Pink
What is the symbol for Iron? What colour does it produce?
Fe
Red, green, blue, yellow
What is the symbol for Cobalt? What colour does it produce?
Co
Blue
What is the symbol for Nickel? What colour does it produce?
Ni
Green
What is the symbol for Copper? What colour does it produce?
Cu
Green, blue
Name 3 gems coloured by Chromium.
Emerald
Ruby
Green jadeite jade
Alexandrite
Red spinel
Name 3 gems coloured by Iron.
Peridot
Almandine garnet
Aquamarine
Blue spinel
Which 2 non-metallic chemical elements can cause colour in diamond?
Boron (B)
Nitrogen (N)
What is ‘dispersion’?
Dispersion is the splitting of white light into the component colours of the visible light spectrum whereby each wavelength is refracted at a differing angle. The measured amount of dispersion in a gemstone is the difference in refractive index of light measured at two different selected wavelengths.
What is ‘diffraction’?
This is a ‘spreading’ effect upon light that occurs when light waves pass an edge, pass through thin slits or very small holes. It can cause interference in white light to produce iridescence.
Describe the spectra. Name the gem material and its colouring element.
Strong absorption edge near 620nm
More or less total absorption of colour other than red
Glass, red (Se (Selenium) Spectrum)
Describe the spectra. Name the gem material and its colouring element.
Single, wide band in the green of moderate strength.
Glass, red (Au (Gold) Spectrum)
Describe the spectra. Name the gem material and its colouring element.
Glass, red (Rare Earth Element (REE) spectrum)
Describe the spectra. Name the gem material and its colouring element.
This distinctive pattern in the blue to blue/green is characteristic for
peridot. If absorption is faint, adjust light level and stone position.
The right band may be wider. In some stones, bands appear as
‘edges’ or even as one wide band.
Three roughly, evenly spaced bands in the blue around 453nm. 473nm. and 493 nm.
Peridot (Fe (Iron) spectrum)
Describe the spectra. Name the gem material and its colouring element.
The bands in the red may appear sharper on one side than on the
other. The absorption in the orange to yellow may be very weak.
There are no obvious lines in the blue.
Emerald (Cr (Chromium) spectrum)
Describe the spectra. Name the gem material and its colouring element.
The line in the red at 653nm allows zircon to be distinguished
from similar stones and is seen in nearly all zircons, including those
that are colourless. Often many lines are seen, with some stones
showing up to 40 sharp lines. Green ‘metamict’ or ‘low’ zircons
may show ‘fuzzy’ lines or bands.
Zircon (U (Uranium) spectrum)
Describe the spectra. Name the gem material and its colouring element.
The width of these bands depends greatly upon the depth of colour and
size of the stone and the brightness of the light. Pale stones may not
show the narrow right-hand band in the green. In dark stones the two
thick bands may merge into one. In cobalt spinel, the bands are ‘thin,
thick, thick’ from left to right. Rare, natural cobalt blue spinel may also
show this spectrum.
Spinel, synthetic blue (Co (Cobalt) spectrum)
Describe the spectra. Name the gem material and its colouring element.
With cobalt glass, the three distinctive bands are more widely spreadout than with cobalt spinel. Usually the widest band is in the red.
Despite that, much red light is transmitted and may be seen through
the Chelsea filter. A similar spectrum is seen with cobalt blue
plastics. Most other blue colourings give no spectrum.
Glass, blue (Co (Cobalt) spectrum)
Describe the spectra. Name the gem material and its colouring element.
An absorption line or narrow band in the blue
A few pale blue natural sapphires and most Verneuil synthetic blue and green sapphires give no absorption pattern at all.
Sapphire, natural blue (Fe (Iron) +Ti (Titanium) spectrum)
Describe the spectra. Name the gem material and its colouring element.
Look for fine lines in the middle of the bright blue (the thicker line may appear to be double) plus the lines in the red. Near the left end of the red, the thicker line may appear to be double. This line may also glow as an emission line, particularly if light is reflected from the stone into
the spectroscope.
Photos; Verneuil synthetic rubies and spectrums. The bottom photo shows a
ruby with an emission line in the spectrum.
Ruby (Cr (Chromium) spectrum)
Describe the spectra. Name the gem material and its colouring element.
The width and darkness of the absorption bands vary considerably.
There is very rarely any line visible in the blue. The number of lines
seen in the red varies with viewing conditions; the thick line may be
seen as a doublet in some stones. This line, and sometimes others
nearby, might appear as emission lines.
Spinel, red (Cr spectrum)
Describe the spectra. Name the gem material and its colouring element.
Yellow is absorbed together with thinner bands at mod-green and
blue-yellow. The latter two may merge into one with dark or large
stones, or insufficient light. Weak bands in the orange and blue are
often seen. Note that this pattern can be seen not only within the
spectra of almandine garnet, but also in other garnet varieties.
Almandine garnet (Fe (Iron) spectrum)
