DINNY HALL GEMSTONES
Gemstones are found in all the colours of the rainbow, and
can range from readily available and easily affordable to
hugely rare and expensive. Carat is the unit of weight used
to measure gemstones, one carat being equivalent to 0.2
grams. One carat can then be divided into 100 points. The
type of gem, its carat weight, colour and clarity all contribute
to its rarity, and therefore its value.
Amethyst
Amethyst is a transparent stone found in shades of purple,
mauve and violet, and is a member of the quartz family.
Quartz is the name given to a crystalline rock composed
of silicon dioxide; it makes up about 12% of the earth’s
crust and is the most abundant mineral on earth. There are
many varieties of quartz, a number of which are gemstones,
and the characteristics are almost infinite.
Other varieties of quartz include Smoky Quartz, which is
transparent brown, Rose Quartz which is opaque and pink,
and Oro Verde a golden green colour.
Green Amethyst or ‘prasiolite’ is now widely
used in jewellery, however this is actually Green Quartz
created by heat treatment of Amethyst.
Fine quality Amethyst is found in Russia, and there is
also a substantial amount in India and Sri Lanka. It can
also be found in Brazil and Uruguay, and at several locations
in the United States.
Aquamarine
Aquamarine is a variety of the mineral beryl and as its
name implies, its finest colour is that of a stunning clear
blue sea. The blue colour is due to traces of iron in the
crystal structure of beryl.
Aquamarine is closely related to emerald, probably the most
well-known member of the beryl family.
Aquamarine is found principally in Brazil and Madagascar,
but other sources include Africa, Siberia, India, Burma,
various parts of the USA, and even the Mourn Mountains of
Northern Ireland.
Diamond
Diamond is the hardest natural material known to man and
can only be cut by other diamonds. Its hardness of 10
means it maintains its polish excellently and resists
scratching, making it ideal for use in jewellery. A diamond
is often assessed using The Four Cs. The
4C’s refer to the Carat, Cut, Colour and Clarity
of the Diamond, all of which play a vital part in determining
the quality, rarity and value.
The round brilliant cut diamond is the most popular;
however other diamond shapes
are also often used. These cuts include the baguette,
emerald, princess, asscher, rose and old cut.
Coloured Diamonds can be found naturally, but this is extremely
rare. These colours include pink, yellow, blue, brown, orange,
black and green. They are referred to as ‘Fancy’
Diamonds and rank amongst the most expensive gemstones in
the world. Heat treated coloured diamonds are also available
at a slightly lower cost.
About 50% of diamonds originate from central and southern
Africa. However, significant sources of the mineral have
also been discovered in Canada, India, Russia, Brazil, and
Australia.
Oro Verde
Oro Verde is a form of quartz; it is transparent and derives
its name from its stunning green and gold colours. Quartz
is the name given to a crystalline rock composed of silicon
dioxide. It makes up about 12% of the earth’s crust
and is the most abundant mineral on earth. There are many
varieties of quartz, a number of which are gemstones, and
the characteristics are almost infinite
Other varieties of quartz include Amethyst, which is transparent
purple, smoky quartz, which is transparent brown, rose quartz
which is opaque and pink.
Lemon Quartz comes from all over the world with some of
the most famous sources including Brazil and Africa.
Rose Quartz
Rose Quartz, a member of the quartz family, is an opaque
stone which exhibits a pale pink to rose red hue. The
colour is usually considered as due to trace amounts of
titanium, iron and manganese.
Quartz is the name given to a crystalline rock composed
of silicon dioxide. It makes up about 12% of the earth’s
crust and is the most abundant mineral on earth. There are
many varieties of quartz, a number of which are gemstones,
and the characteristics are almost infinite.
Other varieties of quartz include Amethyst, which is transparent
purple, smoky quartz, which is transparent brown, oro verde
which is a golden green.
The first crystals were found in the USA, but most crystals
on the market come from Brazil.
Ruby
Ruby is the name given to the transparent red or pink variety
of the mineral corundum.
Corundum can be found in an almost limitless variety of
colours. These include white, and all shades of red, pink,
blue, orange, yellow, green and purple. The colours are
formed by different concentrations of various impurities.
Rubies which have been known for centuries first came to
Europe from Burma, (now known by some as Myanmar). Miners
in the ancient gem mines of Burma have discovered artifacts
to show that the people of the Stone and Bronze Age had
been there before them. Rubies can also be found in Thailand,
Cambodia, Sri Lanka, and at several locations in the United
States.
Sapphire
Sapphire is the most well-known variety of the mineral corundum
Corundum can be found in an almost limitless variety
of colours. These include white, and all shades of blue,
red, pink, orange, yellow, green and purple. Blue corundum
is called sapphire. Other varieties are simply called
sapphire with the colour prefix, as in: pink sapphire.
The colours are formed by different concentrations of
various impurities. Purple sapphires contain traces of
vanadium, while yellow and green sapphires have traces
of iron. Pink sapphires contain traces of chromium. Some
sapphires display pleochroism - meaning more than one
colour in the same stone – changing colour from
shades of blue in outdoor light, to shades of purple in
indoor light.
The best ‘cornflower blue’ colour comes from
Sri Lanka but superb specimens are also found in Kashmir,
and the USA. Other sources include Burma, Thailand, Cambodia,
Australia, Brazil and Africa.
Smoky Quartz
Smoky Quartz is a transparent stone found in shades of brown
to black, it is a member of the quartz family and its colour
is caused by natural (or artificial) irradiation of aluminum-containing
rock crystal.
Quartz is the name given to a crystalline rock composed
of silicon dioxide. It makes up about 12% of the earth’s
crust and is the most abundant mineral on earth. There are
many varieties of quartz, a number of which are gemstones,
and the characteristics are almost infinite
Other varieties of quartz include Amethyst, which is transparent
purple, rose quartz which is opaque and pink, Oro Verde
which is a golden green colour.
Smoky Quartz comes from all over the world with some of
the most famous sources including Brazil and Africa.
Spinel
Spinel is a favorite due to its brilliance, hardness and
wide range of spectacular colours. These include red, brown,
green, yellow, blue, and beautiful pastel shades of pink
and purple. Completely colourless spinel does exist, but
it is extremely rare.
Although now treasured for its own sake, throughout history
spinel has frequently been confused with other gemstones.
There are two particularly famous spinels in the British
Crown Jewels that have been incorrectly identified as rubies.
In addition to Burma, (now known by some as Myanmar)
and Sri Lanka, spinel is mined in Thailand, Tanzania,
the USA, Afghanistan, and Brazil.
Topaz
Topaz occurs in the transparent shades of yellow, orange,
pink, and brown, but also in pale to medium blue, green,
violet and colourless. Orange-red ‘Imperial’
Topaz and pink colours are very rare and most valuable.
It has some relative weakness due to its crystalline structure,
meaning that gemstones have to be handled with care however
this should not pose a problem once the stone is mounted
in jewellery.
Topaz comes from all over the world; however notable occurrences
include Brazil, Pakistan, Russia, and several locations
in the United States.
Tourmaline
This family of gems has one of the largest ranges of colours
available including green, blue, red, pink, orange, yellow,
colourless, brown, and even purple. Most varieties are simply
called Tourmaline usually with the colour specified as a
prefix to the word tourmaline, as in Green Tourmaline. Fine
Pink Tourmaline however is referred to as Rubellite, and
the term watermelon is given to Pink/Green tourmalines that
display pleochroism, meaning more than one colour in the
same stone.
Sri Lanka was an early source of the gem and it is thought
that the sinhalalese word turmali which means ‘stone
of mixed colour’ probably provided the name tourmaline.
Today Brazil provides many colours. Russia, Burma, Madagascar
and parts of Africa are also sources for this gem.
Zircon
The natural color of Zircon varies between colorless,
golden-yellow, red, brown, and green. It is not to be
confused with cubic zirconia, a synthetic substance with
a completely different chemical composition.
Zircons contain amounts of uranium and thorium and can be
dated using modern analytical techniques. The oldest minerals
found so far are zircons from Western Australia, with an
age of 4.4 billion years.
Zircon can be found all over the world, notable occurrences
include Norway, Pakistan, Russia and the USA.
SYNTHETIC AND ARTIFICIAL GEMSTONES
Cubic Zirconia (sometimes referred
to as Zirconia)
Some Gemstones are manufactured to imitate other Gemstones.
The imitations copy the look and colour of the real stone
but possess neither their chemical nor physical characteristics.
The most widely produced of these is Cubic Zirconia, used
both as a colourless and coloured stone to imitate diamond.
At Dinny Hall, the only Cubic Zirconia we use is cut by
hand to Dinny’s design, and is set with 14K Gold.
Laborotory Grown Gemstones
In natural conditions, precious stones are created over
millions of years, but man has found a way to produce, in
a laboratory, stones that are still ‘real’.
Rubies, Sapphires (corundum), Topaz and Spinels can be grown
which are optically, physically and chemically identical
to naturally mined stones. Once cut, the hardness, light
refractive properties and spectacular colour of these lab
grown gems offer a new and delightful alternative to nature’s
own at significantly less cost. We use these laboratory
stones in our Silver Collections.
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