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Archive for the ‘Gemology’ Category

A GUIDE: HOW TO SPOT DIAMONDS FROM ITS SIMULANTS

DIAMONDS: There are certain properties that diamonds possess which can help distinguish diamonds from its simulants, for example, the hardness of diamonds. Diamond is the hardest known material. Such properties can be used as a tool to identify fakes from the real deal with the naked eye or 10x loupe . Here we look at the distinguishing features in both diamonds and the most popular simulants on the market today.

WHAT TO LOOK OUT FOR:

DIAMONDS naked eye and 10x loupe

  1. Diamonds should always have sharp facet edges due to its hardness (facets are the flat polished surfaces on a cut gemstone)
  2. A Bright lustre should be seen (lustre is the way light interacts with the surface, diamond has a adamantine lustre)
  3. A Good polish should be visible on good quality diamonds
  4. Diamonds are singly refractive
  5. Natural diamonds will always contain natural inclusions. Inclusions are a great tool for identifying diamonds from their simulants. Natural diamond inclusions include: Clouds, feathers, needles, pinpoints, crystals, cleavage, bearding, internal graining and dark crystal inclusions. These all aid with the identification of natural diamonds.
  6. The finishing on the girdle of a diamond can be used as an indicator for diamonds. A girdle  is the a edge around the diamond where the top (crown) and bottom (pavillion) of the stone meet. A diamond girdle may have a sugared appearance otherwise known as a ground girdle, it may also be bruted, polished or faceted. Grinding lines should NOT be seen on the girdle of a diamond , if grinding lines are visible then its most likely a simulant
  7. Bearding may be seen on diamonds, these are short and very fine cracks around the girdle
  8. Finally, if there is a large modern stone with good colour and clarity but a poor cut it should raise suspicions

THE IMITATIONS: There are three common simulants of diamonds. These are cubic zirconia, synthetic moissanite and artificial glass. Here we a look at the simulants and their features that distinguishes them from diamonds

WHAT TO LOOK OUT FOR:

CUBIC ZIRCONIA  naked eye and 10x loupe

  1. CZ is the most common diamond imitation
  2. CZ has a lower hardness than diamond so it will show more wear especially around the facet edges and girdle
  3. Facet edges of CZ are less sharp than diamond facets and they  appear more rounded in shape
  4. Chips and bruises will be apparent on the surface of CZ
  5. If the stone is a good size, colour and clarity but a poor cut then you should become suspicious that it’s not a diamond.

MOISSANITE naked eye and 10x loupe

  1. Moissanite  is doubly refractive. This can be used to aid identification because diamond is singly refractive. A doubly refractive stone will show doubling of facets or inclusions which can be seen with a 10x loupe however a singly refractive stone will not show this.
  2. Moissanite will have a slightly green tinge
  3. Parallel needle like inclusion are sometimes visible
  4. Beware with moissanite because it is also a very hard material so facets edges will be sharp. The best way to identify moissanite is through double refraction
  5. Moissanite shows a very high dispersion (this is the stone ability to show different colours when due to the splitting of white light into the colours of a the visible spectrum)

GLASS naked eye and 10x loupe

  1. Glass is very soft material so it will show considerable wear particularly around the facet edges
  2. Chipping will occur as well as conchoidal fractures
  3. Facets will be rounded
  4. Diagnostic inclusions include bubbles and swirls.
  5. Glass will lack the same degree of lustre seen in diamond. It will appear more dull looking.
  6. Mould marks may be visible on the surface of the glass.

This is only a brief guide towards the identification of diamond and its simulants. It does take experience to spot the differences and I advise you to always ask a specialists when buying.

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Following on from the post on pearls I thought it would be a good idea to give a quick lesson on diamonds for those of you who are interested.

First of all there are the 4 c’s. (some of you may already know this)

  1. Clarity
  2. Colour
  3. Cut
  4. Carat
These four factors contribute to the value of a diamond. However, in my opinion, if you want a diamond to be a good investment the most important factors of the 4c’s are the CLARITY and COLOUR and not the size alone.
Lets look into clarity and colour in more detail:
  1. CLARITY

There is a grade system for the clarity of a diamond, it is as follows:
*Inclusions are the imperfections inside a the diamond

  1. 2.   COLOUR

Colour also has a grade system, it begins with D but even colour up to H is of a very good quality. Beyond H a tint of yellow can be seen with a trained eye, the difference is very slight. Here are the grades given to colour in diamonds:

As you can see a tinted yellow colour only begins to show itself after grade H. Therefore H and above are all excellent grades for diamonds. Always use a neutral white background when grading the colour of diamonds and try to stay clear of bright colours.
Extra tips:
  1. There are many convincing diamond simulants out there so be careful, cubic zirconia and moissanite are the most convincing.
  2. Synthetic diamonds are also on the market so watch out for them
  3. Diamonds should show an extremely bright lustre
  4. Diamond is also an extremely hard material so this can help with identifying it. The facets should be sharp around the corners with little to no abrasion.
  5. Always double check with an expert before buying.
I hope this has given you a good introduction to diamonds.

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If you are interested in buying pearls whether natural or cultured here is some basic information to work from:

The 7 factors that you need to take into account when looking for a good quality pearl:

  1. Size
  2. Shape: how round the pearl is, the more spherical and symmetrical the better
  3. Colour: this includes the body colour and the subtle iridescence otherwise known as the orient
  4. lustre: the quality of light reflected from the surface of a material
  5. Surface condition: The smoother the better. Are there any chips, cracks, pits, scratches etc. all effect the value of the pearl
  6. Nacre quality: more useful for cultured pearls, how thick is the nacre, the thicker the better the quality of the pearl surface
  7. Matching: the uniformity of pearls in jewellery
Each of these factors contributes to the value of the pearl.
freshwater loose pearls
Different types of cultured pearls:
  • Akoya: Salt water pearls, cultivated mainly in Japan. Most are a cream colour, typical size 6mm-7mm,
  • South Sea: Salt water pearls, cultivated in Australia, Indonesia and the Philippines. Usually white to golden and range in size from 8mm to 15mm (larger than Akoya pearls)
  • Tahitian: Salt water cultured around the islands of the French Polynesia. Usually black, green, purple and grey in colour. Sizes range from 8mm-14mm
  • Freshwater pearls: Mainly found in china, often pink and orange with a wide range of sizes.
Extra tips!

  1. When grading and looking at pearls always use a neutral grey background and a daylight lamp!
  2. Beware of treatments and imitation pearls.
  3. Most pearls you come across are cultured, natural pearls are extremely rare now days and this is reflected in their price. Natural pearls are rare today because the seas are too polluted for the formation of pearls.
  4. Salt water cultivated pearls are made with a bead nucleus, this can help identify them from natural pearls. However fresh water cultivated pearls do not have a bead nucleus, the only way to distinguish them from natural pearls is by lab testing with the use of X-radiography and X-ray fluorescence.

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