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World of Colour
"The best colour in the whole world is
the one that looks good on you".
Gabrielle Bonheur 'Coco' Chanel (1883-1971)
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Peridot is a 'self
coloured' gemstone
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Yellow Sapphire is an 'other coloured' gemstone
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Now that's some clever advice. As mentioned previously,
colour is the single most important factor when
assessing coloured gemstones. But like everything
to do with beauty, it is highly subjective and at
the end of the day, in the eye of the beholder.
This is not to say that there are no colour paradigms
in gemstones, there certainly are, but these should
never be at the expense of personal preferences.
One thing that confuses me is the stance taken by
some 'experts' with respect to colour preferences.
You should always be aware of how certain colours
are valued in the marketplace, but telling someone
their prized gemstone is not 'true' because of this
or that, not only disregards personal preferences,
it can even turn people off coloured gemstones.
In my mind, the true gemstone connoisseur is an
evangelist never an elitist.
It will come as no surprise that the more attractive
a gem's colour, the higher the value. The most valuable
colours depend on two factors, fashion and rarity.
Fashion is easy to understand, it's all about colour
popularity; if no one finds a gem's colour attractive,
then its rarity really doesn't matter. Inversely,
if a gem's colour is popular and it's rare, such
as Paraíba Tourmaline or Padparadscha Sapphire,
then you've got a gemstone superstar. In general,
intense colours are more favoured than those that
are dark or light, but there are exceptions, for
example, that Victorian favourite, Rose de France
Amethyst.
For most gems, I recommend what I call the 'Goldilocks
Maxim', named after the children's story involving
a juvenile delinquent and three disgruntled bears.
Just like Goldilocks' preferences, the best gems
are not too dark or too light, but just right, with
the intense 'middle' colours being the happy medium.
Most of the time this gauge is reliable, just remember
that the 'intense middle colour' can vary for each
gemstone variety. As the way a gemstone's colour
is described can make people want to own it or avoid
it, some gems have specific words or phrases to
describe their most desirable colours, for example,
'noble red' in Spinel, 'cornflower blue' in Sapphires
or 'AAA' to denote top quality (colour and clarity).
But how does colour actually work? Simplistically,
gemstone colour occurs in two ways:
1.Self Coloured (Idiochromatic): Acolouring
element is incorporated into the mineral's crystal
structure, always giving it a characteristic colour.
For example, Peridot will always be shades of green
from its high iron content, which comprises about
10 percent of its total mass.
2.Other Coloured (Allochromatic): Colour
is caused by small amounts of colouring elements
that are not part of the mineral's normal crystal
structure and/or crystal imperfections (colour centres).
In their pure state, 'other coloured' minerals are
colourless, for example Sapphire. Without colouring
elements (and/or colour centres), all Sapphires
would be colourless.
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Several years
ago, an elderly American lady took the long
bus journey from Bangkok to the gem markets
of Chanthaburi to purchase some Rubies to
pass on as inheritances for her granddaughters.
She was a lovely lady and extremely well-informed.
She'd certainly done her homework, reading
numerous books and speaking to every 'expert'
who'd give her the time of day. In a way,
this was her problem. She had become so
obsessed with finding 'the perfect colour'
that her own preferences had fallen by the
wayside. Each time she got an 'expert opinion',
she got more confused. I brought her back
to earth with a simple question: "Do
you know what Rubies you like?" She
did and within the hour, I thought we'd
narrowed the search, but then she asked,
"Is this the best colour?" In all
honesty, she had selected some beauties,
intense rich-crimson, not too dark, not
too light, so I answered, "For me, yes".
Anticipating, "But not for everyone?"
I added, "These are great collectors'
Rubies and assuming that new deposits don't
miraculously appear and flood the market,
they should hold their value. But don't
you think the most important thing for your
granddaughters will be that you travelled
all by yourself to a small town in Thailand
just to buy them some Rubies you love?"
It is true; sometimes you can't see
the forest for the trees.
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Ruby, the 'king of gems'
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Most things get their react with light. Some gems,
such as Opal, get their colours physically as light
is refracted in flashes of colours that change with
the angle of observation ('play of colour'). But
for most gems, and even most objects, our perception
of colour involves an amazing with transformation.
As revealed by rainbows, white light is comprised
of the individual colours of the spectrum: red,
orange, yellow, green, blue, and violet light. When
white light passes through a gem, some of these
spectral colours are absorbed. The spectral colours
of white light least absorbed combine to produce
the colour of the gem. This absorption of certain
colours is called the 'selective absorption of light'
and is always the same for an individual gemstone.
A red gemstone appears red because all the other
colours of the spectrum except red are absorbed
by the gem. It is changes in a light source's component
colours that cause gems to look different in dissimilar
lighting conditions. Even a small variation in the
light source can produce a big difference in how
we see a gem's colour. In extreme examples, this
results in the colour change effect (click
here for more). While some gemstones
look better in natural daylight and others in artificial
(incandescent) light, a gemstone's colours should
ideally remain beautiful in any light source.
Colour is comprised of three components:
1. Hue is the position of a colour on a colour
wheel. It is described as the shade, tint or sensation
of colour.
2. Tone is the degree of lightness or darkness
of a colour.
3. Saturation is described as the intensity
(strength or purity) of a colour.
Even though there are several industry colour grading
systems (e.g. GemDialogue, GemEWizard and GIASquare),
there is no universal standard for communicating
colour in coloured gemstones. This is mainly due
to coloured gems being highly subjective, resulting
in sellers creating their own grading, such as AAA.
Colour can be a great way to pick the right gem
for you, but please note that colour alone is not
a reliable way to identify gemstones. Even experts
can be fooled. One friend in the industry loves
to reinforce this by routinely showing me examples
of gems that look like something else. I still remember
an exceptionally fine Pezzottaite that at a glance
looked like a Pink Sapphire. Once viewed with a
loupe, its characteristic inclusions gave the game
away. This is an important lesson. Colour helps,
but other visual clues such as inclusion patterns,
signs of wear (hardness), pleochroism, fire and
sparkle are also critical. These features, in combination
with gemmological tools such as a microscope, loupe
and refractometer, are the only way to be certain.
Below, some popular gems are grouped by their colours
- get back in black
(black gems), discover heavenly blues
(blue - violet gems), become a white knight
(colourless/white gems), make them green
with envy (green gems), multiply your choices
(multicoloured gems), warm your heart (red
- pink gems) or simply brighten your day
(yellow - chocolate gems). One question I have been
asked is: "What colour gem suits every person?"
While blue is one of the most popular choices, its
richer tones can be too dark for some people. The
colour of the sky and tropical seas, medium or aqua
blues suit almost any skin tone. Examples include
Aquamarine, Ceylon Sapphire, Paraíba Tourmaline
and Turquoise. Don't believe me? Just look at the
popularity of blue jeans.
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Black
Gems
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Black Diamond |
Black Star Sapphire |
Onyx |
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Other
black gems include Black Spinel, Black
Tourmaline, Hematite and Obsidian. |
| Blue
- Violet Gems |
AAA Aquamarine
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AAA Tanzanite
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Amblygonite
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Amethyst
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Apatite |
Aquamarine |
Blue Diamond
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Blue Fire Opal
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Blue Green
Tourmaline
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Blue Sapphire
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Blue Spinel |
Ceylon Sapphire |
Chalcedony |
Grape Topaz |
Hemimorphite |
Indicolite |
Iolite |
Kanchanaburi
Sapphire |
Kyanite |
Lapis Lazuli |
London Blue Topaz |
Midnight Blue
Sapphire |
Ocean Topaz |
Paraíba Tourmaline |
Purple Sapphire |
Purple Spinel |
Ratanakiri Zircon |
Sky Blue Topaz |
Star Sapphire |
Swiss Blue Topaz |
Tanzanite |
Turquoise |
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Other
blue - violet gems include Azurmalachite,
Blue Moon Quartz, Blue Opal, Cat's Eye
Aquamarine, Sodalite and Sugilite.
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| Colourless/White
Gems |
Diamond |
Goshenite |
Petalite |
White Quartz |
White Sapphire |
White Topaz |
White Zircon
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Other
colourless/white gems include Anglesite,
Aragonite, Calcite, Danburite, Howlite,
Phantom Quartz and White Kunzite .
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| Green
Gems |
AAA Emerald
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Amazonite
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Amblygonite
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Bloodstone
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Chrysoprase |
Colombian Emerald |
Demantoid
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Emerald
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Green Amethyst
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Green Diamond |
Green Kunzite |
Green Sapphire |
Green Tourmaline |
Jade |
Kiwi Topaz |
Malachite |
Moldavite |
Paraíba Tourmaline |
Peridot |
Russian Diopside |
Tsavorite |
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Other
green gems include Aragonite, Azurmalachite,
Chrysocolla, Gahnite, Green Opal, Hiddenite,
Idocrase, Mali Garnet, Merelani Mint
Garnet, Olive Quartz and Prehnite.
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| Multicoloured Gems |
Alexandrite |
Aventurine |
Bi Colour Amethyst |
Bi Colour Citrine |
Bi Colour Quartz |
Bi Colour Tourmaline |
Black Opal |
Cat's Eye Zultanite |
Colour Change Garnet |
Colour Change Sapphire |
Fluorite |
Freshwater Pearl |
Jasper |
Jelly Opal |
Labradorite |
Matrix Opal |
Moonlight Topaz |
Moonstone |
Mother of Pearl |
Mystic Topaz |
Neptune Topaz |
Rainbow Moonstone |
Sardonyx |
Semi Black Opal |
South Sea Pearl |
Tahitian Pearl |
Twilight Topaz |
White Opal |
Zultanite |
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Other multicoloured gems include Bi Colour
Morganite, Boulder Opal, Cat's Eye Alexandrite,
Fire Agate, Mabe Pearl, Mookite, Rainbow
Quartz, Scapolite, Snowflake Obsidian
and Spectrolite.
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| Red
- Pink Gems |
Cherry Topaz
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Flamingo Topaz
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Kunzite
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Morganite
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Mozambique Garnet
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Mulberry Topaz
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Noble Red Spinel
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Pink Diamond
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Pink Sapphire
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Pink Spinel
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Pink Tourmaline
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Pyrope
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Red Diamond
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Rhodochrosite
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Rhodolite
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Rhodonite
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Rose de France
Amethyst
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Rose Quartz
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Rubellite
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Ruby
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Star Ruby
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Tanzanian Ruby
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Other red - pink
gems include Andesine, Bixbite, Clinohumite,
Pezzottaite, Pink Opal and Umbalite.
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| Yellow
- Chocolate Gems |
Agate |
Amber |
Andalusite |
Canary Topaz |
Carnelian |
Cat's Eye Chrysoberyl |
Champagne Diamond |
Chrysoberyl |
Citrine |
Cuprian Tourmaline |
Fire Opal |
Heliodor |
Hessonite |
Imperial Topaz |
Marcasite |
Lemon Citrine |
Mandarin Garnet |
Orange Sapphire |
Padparadscha Colour Sapphire |
Padparadscha Sapphire |
moky Quartz |
Spessartite |
Sphene |
Sunset Sapphire |
Sunstone |
Tigers Eye |
Yellow Diamond |
Yellow Sapphire |
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Other
yellow - chocolate gems include Andradite,
Bronzite, Cat's Eye Scapolite, Cat's
Eye Sillimanite, Cognac Quartz, Epidote,
Idocrase, Kornerupine, Malaia Garnet,
Orthoclase, Quartzite, Rutile Quartz,
Sard, Scheelite, Sillimanite, Star Diopside,
Star Sillimanite, Star Sunstone, Unakite,
Yellow Beryl, Yellow Kunzite and Yellow
Opal.
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