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Coloured gemstones |
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Every gemstone is unique and Gowan Jewellers is happy to provide
a selection of stones
on approval for you to view at the shop. You can then
see the differences in colour, clarity, size and shape for yourself,
according to your requirements and budget. We are happy to give advice
with regard to the suitability of different stones for certain designs. This
page is a guide to
the most popular gemstones with a few examples shown and their general
properties explained
but if you have any questions please contact us by telephone or email for
free, professional advice.
You will be
under no obligation to buy. |
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Emerald belongs to the beryl group together with
aquamarine.The name derives from the Greek Smaragso, which means 'green stone'.
Only the
finest qualities are transparent. Often the emerald is clouded by inclusions
(liquid or gas bubbles, healing cracks and foreign crystals). These are not
necessarily classified as faults, but are evidence as the the genuineness of the
stone as compared with synthetic and other imitations. The expert refers to
these inclusions as a 'Jardin' (garden). The most desired colour is a deep green
which is more valuable, even with inclusions, than a pale and clean quality.
All emeralds are brittle and combined with internal stress, sensitive to
pressure. They can chip on impact, so emeralds should not be worn everyday.
Emeralds should never be cleaned with steam or any cleaning solution that
includes ammonia. Most "jewellery cleaner" is not compatible with the oil
treatment of Emeralds. To clean Emeralds use warm soapy water and a soft
toothbrush. Never use an ultrasonic to clean Emeralds. |
  
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Sapphire
belongs to the corundum group, which has
excellent hardness with 9 on the Mohs scale (exceeded only by that of the
diamond) so that sapphires are easy to look after and suitable for everyday
wear. Corundum is a pure aluminium oxide which
crystallised into wonderful gemstones a long time ago as a result of
pressure and heat at a great depth. The presence of small amounts of other
elements, especially iron and chrome, are responsible for the colouring,
turning a crystal that was basically white into a blue, red, yellow, orange,
pink, purple or greenish sapphire. The Kashmir colour is considered the most
sort after sapphire - a pure, intense blue with a very subtle violet
undertone, which is intensified yet more by a fine, silky shine. There are a
wide range of fancy colours in addition to blue, for example an orange
variety with a fine pink undertone called 'padparadscha', which means 'lotus
flower'. Star sapphires are another rarity, cabochon cut with a starlike
light effect which seems to glide across the surface of the stone when it is
moved.Sapphires are found in India, Burma, Ceylon, Thailand, Vietnam,
Australia, Brazil and Africa. |
 
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Ruby is the red variety of the mineral
corundum, of which the sapphire is also a variety, and so is also very hard
with good brilliance. Slight traces of elements such as chrome, iron,
titanium or vanadium are responsible for the colour. Some rubies display a
wonderful silky shine, the so-called 'silk' of the ruby. This phenomenon is
caused by very fine needles of rutile. In the rare star rubies it is these
crystals that cause a captivating light effect known as asterism creating a
six-spoked star. India was historically the ruby's country of origin
and the word 'corundum' is derived from the Sanskrit word 'kuruvinda'. The
most prized colour is known as 'Burmese' after the famous deposits in Burma
(now Myanmar): a rich, full red with a slightly bluish hue, referred to as
'pigeon-blood red', exceptionally brilliant in natural or artifical light.
Those from Thailand are a muted darker brown red 'Siamese colour'.
Some cheaper commercial rubies have been heat treated to improve their
colour but has to be disclosed at sale. |
 
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Opal is divided into 3 groups: the opalescent precious
opals, the yellow-red
fire opals and the common opals.The name is derived from an Indian word for
"stone". Their physical properties vary considerably. Within the
precious opal family there are three types of opal: Doublet, Triplet and Solid.The special characteristics of the precious opals is their opalescence, a
rainbow-like iridescence which changes with the angle of observation. Opal
always contain water, the content varies but it can be as much as 30%. Over time
the stone can loose water, resulting in cracks. To avoid this aging process
store opals in cotton wool. The microscopic crystaline structure of opal
consists of tiny spheres and therefore the stones are sensitive to pressure and
knocks. We advise that opal jewellery is reserved for special occasion wear to
avoid damage. To clean opals use warm soapy water with a soft toothbrush or
cloth, Doublets and Triplets should never be soaked or immersed in water. Never
use an ultrasonic to clean opals. It is advised to avoid extreme temperatures.
If unsure on how to clean your opal you are welcome to bring it into the shop |
 
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Aquamarine
since ancient
times, has been regarded as the sailors' lucky stone. Its name is derived from
the Latin 'aqua' (water) and 'mare' (sea). It is in the same mineral group as
emerald but is almost entirely free of inclusions, has good hardness (7.5 to 8
on the Mohs scale) and a wonderful shine. It does not scratch easily and is
suitable therefore for everyday wear. Iron is the substance which gives
aquamarine its colour, a colour which ranges from an almost indiscernible pale
blue to a strong sea-blue. The more intense the colour of an aquamarine, the
more value is put on it. Clear large blue stones with
immaculate transparency
and magnificent shine are considered the best
and some also have a light greenish
shimmer. The best large stones are usually from Brazil but other deposits are in
Nigeria,
Zambia, Madagascar, Mozambique, Afghanistan and Pakistan. Aquamarines are ideal
for contemporary unusual cutting due to the large crystal size and lack of
inclusions. |
 
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Tourmaline are mixed crystals of aluminium boron silicate with a complex composition,
slight differences in which cause completely different colours. Crystals of only a single
colour are fairly rare; indeed the same crystal will often display various
colours and various nuances of those colours. And the trademark of this gemstone
is not only its great wealth of colour, but also its marked dichroism. Depending
on the angle from which you look at it, the colour may be different or more or
less intense.
The name
tourmaline comes from the Singhalese words 'tura mali' meaning 'stone with mixed
colours', referring to the colour spectrum of this gemstone, which outdoes that
of all other precious stones. A blue /violet colour is sort after and
those showing red/pink to green colours are sometimes referred to as
'watermelon'. It is relatively hard wearing, 7 to 7.5 Mohs scale and does
not chip or fracture easily. |
 
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Tanzanite is an unusual and rare gemstone because it
occurs in only one place worldwide, the East African state of Tanzania, and was
only discovered in 1967.Tanzanite is a blue variety of the gemstone zoisite. It
consists of calcium aluminium silicate and is not particularly hard, having a
value of 6.5 to 7 on the Mohs scale, it also has 'easy cleavage ' in one
direction meaning an unlucky knock can cause it to fracture. For that reason, it
should always be worn carefully and never placed in an ultrasonic bath. The deep
blue of the tanzanite is fantastic, and runs from ultramarine blue to light
violet-blue. The most coveted colour is a blue surrounded by a delicate hint of
purple. It is thought that all deposits of this gem will be exhausted within
twenty years and therefore larger stones can be considered as an investment
opportunity. The best stones are often certificated in a similar way to diamonds
with 4 colour intensity grades from Vivid to Pale, clarity and cut grades. |
 
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Amethyst
has a name derived from the Greek "amethystos", which means "not intoxicated", as
in antiquity it was believed to ward off drunkenness. Discoveries of huge
Amethyst deposits since the 1800's have made Amethyst fairly inexpensive and
very obtainable. Amethyst colours range from light pinkish violet to dark
purple, and the transparent deep purple colours are the most highly regarded. It
is a variety of Quartz with the colour caused by
iron constituents in
connection with natural radioactive radiation.
It is found worldwide with main deposits found in Brazil, Uraguay and
Madagascar. It has a hardness of 7 on Moh's scale and larger stones often
show different areas of colour intensity. Amethyst can change colour when heated
or left in strong sunlight. |
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Citrine is another form of silicon dioxide the same
as Amethyst and the yellow colour does occur naturally with the presence of
iron. Historically,
it has been found in Spain, on the Scottish island of Arran, in France, Hungary
and in several mines worldwide.
However most commercial citrines are actually heated
treated amethysts. It is sometimes confused with topaz being sometimes mis-named
as 'golden topaz'.
The colours range from a lemon yellow to gold-brown.
A bi-colour form with the purple quartz amethyst is
known as Ametrine. The hardness is 7 on Mohs scale and it does not crack easily
although it is not a very 'brilliant' gemstone but has a mellow warm tone.
The Quartz group of gemstones is a large one including the leek-green
Prasiolite, delicate pink Rose Quartz, colourless Rock Crystal,
bluish white/grey Chalcedony , brown-red Cornelian, apple-green
Chrysoprase, strpied/spotted Jasper and the Agates. |
 
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Garnet
is most often
encountered in it's deep warm red colour, but also exists in various shades of
green 'Demantoid', a gentle to intense yellow 'Grossular' , a fiery orange
'Mandarin' and some fine earth-coloured nuances 'Spessarite'
. The deep warm red colours are often
described as African garnets and the pinker hues are Rhodolites.
The name means 'the grainy one', coming from the Latin 'granum', for grain,
referring to the typical roundish shape of the crystals.
The garnet gemstone group has similar
chemical compositions of aluminium silicate, has 7 to 7.5 Mohs hardness and high
brilliance due to a high refractive index. Historically
garnet was popular as a
talisman and protective stone, as it was believed to light up the night and
protect its bearer from evil and disaster. Garnets are found worldwide. |
 
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Tsavorite is a green grossularite, a
mineral belonging to the colourful gemstone group of the garnets. It was
discovered in 1967 in the East-African bushland along the border between Kenya
and Tanzania. It is named after the Tsavo National Park, with its abundance of
game, and the Tsavo River which flows through it. It has an
extraordinarily beautiful colour and good transparency. The colour range of the
tsavorite includes its vivid, radiant green, a springlike light green, an
intense blue-green and a deep forest green. It has particularly high refractive
index (1.734/44) giving great brilliance. The hardness of 7.5 on Mohs
scale and lovely colour make it similar to emerald but without the disadvantage
of being likely to crack or splinter as a result of an incautious movement, as
with emeralds. Stones over 2 carats are very rare. |
 
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Topaz
is a fluorine aluminium
silicate and comes in yellow, yellow-brown, honey-yellow, flax, brown, green,
blue, light blue, red and pink ... and sometimes it has no colour at all. The
most common colour seen is yellow sometimes called 'precious topaz' to
differentiate it from citrine, or pale to intense blue called 'Sky' or 'London'
blue (usually heat treated and irradiated colourless topaz). The pink is the
most valuable.
It has been known for 2000 years and in antiquity was believed to
serve in protection against enemies and as a symbol of beauty and splendour. It
is very hard, and has good brilliance but with 'perfect cleavage' can fracture
with an unlucky blow. Imperial topaz is yellow,
pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have
a bright yellow to deep golden brown hue, sometimes even violet. In the 18th
century a famous mine was in Germany, now is found worldwide such as US,
Cornwall, Australia, Russia, Japan and Mexico! |
 
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Kunsite is a delicate pink to violet gemstone named
after G.F.Kunz who first described it in 1902, when it was discovered in
California. The appeal of this gemstone lies in its clarity and its fine
delicate pink nuances which often display a hint of violet. Some kunzites from
finds in Afghanistan display a rich, strong violet, a light violet and a light
green depending on the angle of observation. In gemmology, this phenomenon is
known as pleochroism, the meaning of which equates to 'multi-colouredness'. As a
variety of spodumene, kunzite belongs to the class of the chain silicates. It
has minute traces of manganese to thank for its fine lilac colour. However, the
colour can fade in direct sunlight. For that reason, jewellery with kunzite
should never be worn while sunbathing or on the beach. Its hardness is fairly
good, between 6.5 and 7 on the Mohs scale, but perfect cleavage and is thus
extremely difficult to cut. The more intense the colour, the more valuable the
kunzite. Kunzite is said to enhance a
person's capacity for devotion and understanding and to bestow inner peace. |
  
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Peridot is usually a vivid green with just a hint of gold. It is
a very old gemstone found in ancient Egyptian jewellery.The ancient Romans too
were fond of this gemstone and esteemed its radiant green shine, which does not
change even in artificial light. For that reason they nicknamed it the 'emerald
of the evening'. The name is derived from the Greek word 'peridona', which means
something like 'to give richness'.In the 1990's a sensationally rich and fine
deposit was found in Pakistan, now known as 'Kashmir peridots'. The peridot is
one of the few gemstones which come in one colour only. The rich, green colour
with the slight tinge of gold is caused by very fine traces of iron. From a
chemical point of view, peridot is an iron magnesium silicate. The intensity of
the colour depends on the amount of iron actually present. Peridot is not
particularly hard - only 6.5 to 7 on the Mohs scale - but it is easy to look
after and fairly robust. It is also found in Myanmar, China , Africa and
Arizona. |
 
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Zircon
comes in a wide range of different colours
but for many years the most popular was the
colourless variety, which looks more like diamond than any other natural stone
because of its brilliance and dispersion.
The name probably comes from the Persian word 'zargun', which means
'gold-coloured but the most
popular colour is a pastel blue zircon. It is also available in green, dark red,
yellow, brown, and orange.
'Hindu
poets tell of the Kalpa Tree, the ultimate gift to the gods, a glowing tree
covered in gemstone fruit with leaves of zircon. In
the middle ages, zircon was said to aid sleep, bring prosperity, and promote
honour and wisdom in its owner.
Natural zircon today suffers on account of the similarity of its name to cubic
zirconia, the laboratory-grown diamond imitation. Zircon is mined in Cambodia,
Sri Lanka, Thailand, Myanmar, Australia, and other countries. It is one of the
heaviest gemstones with very high brilliance and strong double refraction but is
brittle and can chip easily. |
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Wedding Anniversary Stones
1. - Freshwater Pearls
2. - Rose Quartz
3. - Rock Crystal
4. - Amethyst
5. - Turquoise
6. - Garnet
7. - Onyx Marble
8. - Tourmaline
9. - Lapis Lazuli
10. - Black Onyx
11. - Haematite
12. - Agate
13. - Malachite
14. - Opal
15. - Crystal
20. - Platinum
25. - Silver
30. - Pearl
35. - Coral or Jade
40. - Ruby
45. - Sapphire or Alexandrite
50. - Gold
55. - Emerald
60. - Diamond
65. - Star sapphire |
Birthstones & their
Symbolic/Mythological meanings
January -
Garnet : protection from evil & illuminates the night.
February - Amethyst : intelligence, piety & an antidote to
drunkeness !
March - Aquamarine : marital happiness, joy & wealth.
April - Diamond: innocence, eternity & health.
May - Emerald: love ,good luck & well-being.
June - Pearl : peace, nobility & beauty.
July - Ruby : love, passion & strength
August - Peridot : success & plenty.
September - Sapphire : sincerity, loyalty and faithfulness
October - Opal : healing, true love & an anti-depressant!
November - Topaz : strength, clear-sightedness & & dispels
enchantment!
December - Zircon : prosperity, honour & wisdom. |
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