Traditionally, there are only four stones classified as 'precious' gems. They are: Diamonds, Rubies, Emeralds, and Sapphires. All other stones are classed as 'semi-precious'.
The terms 'PRECIOUS' and 'SEMI-PRECIOUS' are only traditional, historic classifications. Some semi-precious gems may be more valuable than some precious gems.
A gemstone's value is determined by its rarity, its colour, the size and cut of the stone, the absence of any flaws and the clarity of the gem.
Gemstones are usually measured by weight in CARATS. This is the same term as used to indicate the purity of gold in alloy. When referring to the weight of gemstones, carats are broken down into points. There are 100 points to one carat. One carat weighs only one-fifth of a gram.
Most gemstones used in jewellery are cut into various shapes, such as pear, oval and square. The cutting of the gem is very important as it can INCREASE the value by emphasising the colour and reducing or eliminating any imperfections.
Perhaps the most important function of cutting the gem is to increase the light reflecting qualities of the stone. Tiny flat surfaces, called FACETS, are cut onto the surface of the stone. The most common cuts of diamonds and cubic zirconias have 58 facets. It is these facets which give the gemstones their sparkle.
Diamonds
Diamonds are the hardest substance known to man and the most highly prized of gemstones.
A diamond is a transparent gem made of pure carbon that has been crystallised by nature over many millions of years. It is many times harder than Corundum, the next hardest substance we know, of which rubies and sapphires are formed.
Many people think diamonds are unbreakable, this is not so. A diamond crystal structure, like the grain in wood has 'hard' and 'soft' directions. A blow of sufficient force, in a very exact direction, can crack, chip or split a diamond. This is an important factor in the cutting of diamonds. This is done with a diamond saw, and can take hours to cut even small stones. The many facets are cut at exact angles to enhance the brilliance of the stone.
As light enters through the top (table) of the stone it reflects off the pavilion (side) facets to create that sparkle you see in diamonds.
There are 58 facts on a brilliant cut diamond, the bet cut available, however the most time consuming and therefore the most costly.
Discriminating people appreciate quality. The thought of purchasing a home, a car or even a bottle of fine wine that is anything short of what they really want would be unheard off. The same holds true with diamonds (and jewellery in general). Two diamonds that look alike at first, may in fact, be very different. And two diamonds of equal size can have very unequal values. The differences can be subtle indeed. To understand these differences is to understand the 4 C's:
CUT: Many people confuse cut with the shape of a diamond. The shape is largely a matter of personal preference and does not necessarily effect the value. However, it is the cut that enables a diamond to make the best use of light. When it is cut to food proportions, light is reflected from one facet to another and then dispersed through the top of the stone. If the cut is too deep, some light escapes through the opposite side of the pavilion. If the cut is too shallow, light escapes through the pavilion before it can be reflected.
COLOUR: Good colour is no colour. Because it is the totally colourless diamond that acts as a prism, allowing light to pass effortlessly through the diamond and be transformed into rainbows of colour. There is a colour grading scale from totally colourless to light yellow. The differences between one grade and another are very subtle.
However, there are coloured diamonds as well. The West Australian Argyle stones are famous throughout the world and because of the rarity of pink, green and yellow diamonds their price can be very high.
CLARITY: Diamonds, more than any other gemstones have the capability to produce the maximum amount of brilliance. And one that is virtually free of interior or exterior inclusions (also known as flaws) is of the highest quality, for nothing interferes with the passage of light through it. These imperfections of crystallisation take the form of tiny bubbles, clouds, cracks or feathers and mineral inclusions. They are not structural weaknesses, but do detract from the brilliance of the stone.
CARAT: Weight. This is the size of the diamond, measured in carats. Size is the most obvious factor in determining the value of a diamond. But remember value really depends on the quality.
Peridot
A beautiful, warm, soft olive or yellowish-green gem. It is surrounded by superstition. It was once thought to break evil spirits. The gem was associated with the sun, whose rays gave lie and dispelled the mysteries of darkness. It was considered an aid to friendship and was also believed to free the mind of envious thoughts.
Peridot is not a hard stone, 6 on the Mohs Scale, so some care needs to be taken not to scratch it, as it would lose its brilliance. It can be found in Australia, Burma, Arizona, Brazil and Czechoslovakia and is the birthstone for August.
Blue Topaz
The symbol of love and affection, an aid to sweetness and disposition. It has become very popular in recent times, as it closely resembles Aquamarine. Topaz is a relatively hard stone reaching 8 on the Mohs Scale of relative hardness, of which the Sapphire and Ruby are 9 and the Diamond is 10. Many rough Topaz stones are heat treated to darken the colour and it is impossible to tell which ones are. This does not harm the stone, but naturally enhances the colour.
Sapphire
It's the name for all colours of the corundum family, except red. Colours include pink, yellow green, golden orange, purple, green, colourless and blue. It is thought to be the stone of the soul, preserves the wearer from envy and attracts divine favour. Sapphires are mined in many parts of the world such as Sri Lanka, but, Australia is now a very large supplier of the world's sapphires, where they are found mainly in NSW and QLD. All of Amber-Jewels sapphires are purchased in Australia.
Ruby
The word "Ruby" derives from the Latin Rubinus, meaning red. As you may well know, it belongs to the corundum family and is composed of Crystalline Aluminium Oxide. It is the presence of less than 1% Chromic Oxide that gives it the distinctive colour. Ruby is probably the rarest of all gemstones, a Ruby of 5 carats would truly be expensive.
Because of its colour being associated with blood, it is said to protect the wearer from all ailments associated with the blood. It is also thought to remove evil thoughts. Associated with passion, the Ruby is believed to control it and is also credited with being able to solve disputes.
Emerald
Emeralds have a long and romantic history. Nearly 4000 years ago it was bought and sold in Babylon, the world’s earliest known gem market. It has been associated with Venus, the Goddess of love. It was regarded as the symbol of immortality and supposed to be beneficial to the eyes.
Just a few years ago, rich deposits of Emerald have been found in Brazil, and the reopening of Zambian mines has resulted in a good supply of emeralds. Really fine Emeralds are rare and very costly gemstones. Other sources for Emeralds are Russia, India and Colombia.
Emerald is a silicate of Berylium and Aluminium, which owes its grass-green colour to the same Metallic Oxide, Chromic Oxide, which is responsible for the colour of Ruby. Emerald crystals are usually heavily marked with inclusions and surface cracks are often present. Emeralds have a marked tendency to split and they are, therefore, tricky stones both to cut and set. To protect them during cutting and also to enhance their appearance, it is common practice to oil the crystals using paraffin or machine oil. This oil not only heals the surface cracks, but also gives the stone its velvety appearance. The snag of oiling, is that it is possible to leach out the oil by cleaning the stone ultrasonically in a warm solution.
Emeralds are a quite hard stone at 7.5 on Mohs Scale, so they are a good ring stone.
Garnet
Garnets are a fairly common semi-precious gemstone and it is only this abundance that prevents them from being more valuable than they are. Garnets can be very attractive and they are found in a huge variety of colours, from red all the way through to green & blue.
Garnets enhance the will power and perseverance, comforts and helps depression, strengthens the heart. Revitalises the bloodstream and enhances the imagination.
They are the birthstone for January and symbolize constancy.
Citrine
A citrine is a glassy yellow variety of quartz, because of its colour it can be confused with a yellow topaz.
It is said to relieve tiredness, bring happiness and strengthens the nerves. It is good for the kidneys, colon, liver, gallbladder, digestive organs and the heart. Diminishes self destructive tendencies and raises self esteem.
Pearl
Classed as a semi-precious gem, pearls are not stones at all. Pearls are formed in an oyster when a bit of sand or other impurity irritates the oyster, causing it to secrete a substance known as NACRE [commonly called, mother of pearl] around the irritation. Most of today’s pearls are now grown in pearl farms and are called CULTURED PEARLS.
Another type of pearl is the FRESHWATER PEARL which, as the name suggests, comes from oysters which live in fresh water as opposed to salt water. Freshwater pearls often come in irregular shapes which are called BAROQUE PEARLS.
Cubic Zirconia
Cubic Zirconias are man-mad diamonds, not natural gemstones. However, although they are imitation “diamonds” they are not made of plastic or glass and are relatively expensive stones. They are made by subjecting common graphite to extremely high temperatures and pressure. This is much the same way Mother Nature makes diamonds. The result is a stone which is almost identical to a natural diamond, without the expense. Special tools are used t tell them apart.
Being man made, they exhibit the qualities of the finest, most highly prized flawless diamonds. They are clear, almost colourless and flash brilliantly by reflecting light in the same manner as diamonds. One reason people believe they can tell the difference between cubic zirconias and diamonds is because most people have never seen a top quality, flawless diamond and have difficulty believing the fir and brilliance of a cubic zirconia.
Cubic zirconias should not be confused with Zircons, which were the original man-made diamond and had a tendency to loose their brilliance and go milky. Cubic zirconias actually weigh a little more than a comparably sized diamond and it is about .05% less hard.
Opal
Opal could be called Australia's national gemstone. The best quality opal is just as valuable as any 'precious' gemstone and the extraordinary variety of colours and opal exhibits since Roman times.
