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Sell Diamonds Using Our Diamond Valuation Guide

Here at WP Diamonds we assess thousands of diamonds a week. Each diamond is over 1 billion years old and is as unique as a fingerprint. When looking to purchase a diamond people can spend a lot of time researching and learning about diamonds, in order to understand what makes them so valuable. It is as important to us that you do the same when you are looking to sell your diamond as we want you to be confident that you are getting the right price and the right service levels.

Diamond Valuation Guide

Below is a guide to selling your diamond, which follows the steps we take to look the attributes to enable us to give the most competitive price to the customer.

Step 1. Identifying the Shape and Cut

The shape of the diamond is a very important when it comes to putting a value on your diamond. Round Brilliant cut diamonds tend to carry a higher premium than other fancy shapes.

WP Diamonds will pay up to a 30% premium for an excellent cut diamond. The excellent cut diamond will be assessed using our knowledge of the GIA cut grade system, when our buyer evaluates the diamond they will use their expertise to decide what ‘cut grade the diamond would be assigned by the GIA when it is sent for certification.

How Can We Tell If The Diamond Is Round?

The truth is that many diamonds we see here at WP Diamonds have not been cut using the technology and precision available to cutters today. This will often mean that the diamonds are not exactly round, the ‘table’ of the diamond is not in the middle of the stone and the facets are not symmetrical. These diamonds may have to be re-cut for us to be able to sell them back into the marketplace.

Step 2: Assessing The Condition Of The Diamond

Diamonds are the hardest natural substance known to man, so generally they are still in good condition even after they have been worn in jewelry. However, this is not always the case. Diamonds have four directions in which they will easily cleave (break) and cutters actually use this property to help cut the diamond crystals.

It can be the case that the diamond could have been damaged during the process of being set into an item of jewelry, and sometimes even the setting itself can put a lot of pressure on a diamond. Unfortunately a slight knock in the wrong place can cause a diamond to split, this often happens to the corners of princess cuts, and the culet (the point at the bottom of the diamond). If the diamond is damaged our experts will decide how much weight it may lose when we re-cut back to its perfect proportions and will then value it accordingly.

Step 3: Estimating The Diamond Weight

Most diamonds we receive at WP Diamonds will be set in jewelry. We will estimate the weight of the diamond by measuring the diamonds diameter and depth right down to the millimeter. There are various tools available to us that use mathematical formulas to calculate very accurately the estimated weight of the diamond.

Diamond prices are based on the weight of the diamond. There are price jumps at particular weight brackets. For example, a 0.99ct H SI1 may trade at $5400/ct, where as a 1.00ct H SI1 may trade at $6700/ct. It is therefore unlikely a cutter would cut the diamond to 0.99ct, they are more likely to compromise the cut of the stone and retain the weight. If we estimated the diamond weight to be 0.99ct, then we are likely to ask the customer if we can remove the stone from its setting and weigh it, because we want to pay the best price possible.

Step 4: Clarity Grading

All of our WP Diamonds graders are trained to grade to GIA standards. The GIA is one of the most trusted diamond grading laboratories in the jewelry industry, and their standards are internationally recognized. Most of the diamonds we buy at WP Diamonds are sent to the GIA for certification before we sell them. It is very important to WP Diamonds that our graders are trained to

the highest standards, enabling them to accurately assess your diamond and therefore allowing us to purchase it for the very best price possible. In fact, in a recent survey conducted by WP Diamonds, we found that in over 85% of cases reviewed, WP Diamonds’ appraisals corresponded exactly with the GIA grading reports received. .

What is A Color Clarity Assessment?

When assessing the clarity of a diamond, the grader is actually looking for inclusions (or blemishes) either on the surface of the diamond or within the diamond itself. Inclusions are particles that have been trapped within the diamond as it was forming in the earth millions of years ago. Each diamond and its inclusions are as unique as a fingerprint, and the inclusion proves that the diamond is natural and not man made.

Clarity grading is carried out using a loupe with 10x magnification. The grader will assess the diamond through as many different facets as possible, making sure they have seen all the inclusions within the

stone and identifying any blemishes on the surface of the stone. There are many different types of diamond inclusion, and if you have the diamond certified, they are normally identified on a diagram on the certificate so that an evaluator can clearly see where the inclusions are to be found on the diamond. They range from pin points and needle like inclusions through to other minerals within the diamond such as a Garnet, sometimes you even find a diamond crystal within the diamond. Having carefully evaluated the diamond using their extensive diamond grading knowledge, our graders will then allocate one of the GIA’s 11 clarity grades to the diamond.

Step 5: Checking The Girdle

The girdle is the edge between the top and bottom of the stone that helps protect the stone from chipping. The grader will check the girdle condition after assessing the stones clarity. In doing this they will be checking for thickness, condition and laser markings along the girdle.

Girdle Factors

  • Thickness – A girdle that is too thick can make the stone look unattractive and could also affect our estimated weight of the stone. The girdle is there to protect the diamond so it should be thick enough to prevent chipping but not so thick that it is unsightly.
  • Condition – Diamonds girdles are finished in 3 ways.
    • Bruted – is the natural state of the rough diamond, so it has not been altered during the cutting and polishing process, it appears misted.
    • Polished – when the diamond was polished they chose to polish the girdle as well as making it shiny. Faceted – tiny little flat facets have been put onto the girdle during the cutting process.
    • Laser Markings– Often Gem Laboratories will laser a tiny logo and certificate number onto the girdle of the diamond. This does not affect its clarity grade in any way. If the graders find a number this means they may be able to track the grading report or certificate, and will then have access to the detailed characteristics of the diamond. It is also possible to have messages lasered onto the girdle, which can be polished off before WP Diamonds trades the diamond.

Step 6: Checking for Treatments

A treated diamond is a diamond that has had its appearance altered by manmade means, usually to improve the diamonds color or clarity, or both. Treatments always affect the value of a diamond. In fact, laser-drilled and fracture-filled treated diamonds are valued at half the price of a natural untreated diamond. Other treatments will also affect the price.

There are a variety of treatments that can be carried out on a diamond, a small number of which can only be detected by a Gemological Laboratory; however, most can be detected very easily by our team of graders using a loupe and many years of experience. Two of the most common treatments that our graders come across are laser drilling and fracture drilling.

Laser Drilling

This is usually carried out on a diamond with black inclusions within the diamond. During this treatment the diamond is subjected to a laser which drills down to the unsightly inclusion and usually burns the inclusion out. If this does not get rid of the inclusion, the diamond is placed in a vacuum and acid is poured into the tiny hole in order to bleach the inclusion out. This process improves the clarity of the diamond, but can be detected by skilled diamond graders quite easily. (Before and After Laser Drilling)

Fracture Filling

This treatment is usually carried out on diamonds with surface-reaching inclusions, these are known as fractures. Again the diamond is placed into a vacuum and acid is poured into the fracture, bleaching the surface inclusion. From here glass is drawn into the fracture to fill the gap. This process improves the clarity of the diamond, but the treatment can easily be detected by skilled diamond graders.

Step 7: Checking the Color Grading

The internationally accepted color scale, which was created by the GIA, starts at the letter D (which is the whitest color) and ends in Z (the most tinted with color). There are two color ranges in the diamond world. The most depicted is the Cape series, which shows as a yellow tint. There is also a brown series, which shows a brown tint. The brown tinted diamonds are less sought-after and therefore tend to fetch a lower value than the yellow.

Once we go beyond the end of the color scale, the diamonds would then move into the fancy colored diamond range. They consist of the colors yellow, pink, brown, blue, green, red, and orange. This is referred to as the hue of a diamond.

Looking at a loose diamond (i.e. when it is not set in jewelry) is the most accurate way to grade a diamond for color, and it takes a lot of experience to color grade. Once a diamond is loose, our graders can clean it and can then compare it on a color-grading tray in order to enable them to give it an accurate color grade. The process consists of turning the diamond upside down in a white color-grading tray and looking at the body color through the side of the stone. The reason graders do not look at the diamond from the top, is because the reflections from the diamond would interfere with their eye, therefore impeding their ability to assess the body color accurately.

Using Master Stones In Color Grading

Master stones are often used in order to grade the color of a diamond. These master stones are a set of diamonds or – sometimes even cubic zirconia – which have been produced and graded to GIA standards so that the grader can make a direct comparison with a color master stone in order to help determine the color of the diamond being assessed. Once the grader has assessed the stone from all angles, they will then allocate one of the GIA color grades to each diamond.

Looking at diamonds set in jewelry also takes a lot of experience. Furthermore, it is often more difficult with settings that surround the entire diamond as the light cannot pass through the diamond as easily. The color of the metal can also interfere with the appearance of the diamond, but an experienced grader will have the ability to grade the color despite this. It is also very important to make sure the diamond is clean as dirt will also interfere with the body color of the diamond.

Step 8: Checking For Fluorescence

A small percentage of diamonds have fluorescence. This means that they glow when stimulated by long-wave Ultra Violet light. The majority exhibit blue fluorescence but sometimes diamonds may fluoresce pink, orange, green or red. When measuring a diamond’s fluorescence, it is spilt into the following categories: None or Nil, Faint, Medium, Strong and Very Strong.

Generally, most fluorescence has little to no effect on the appearance of the diamond. Occasionally strong or very strong fluorescence may make the

diamond appear cloudy and an experienced diamond grader could tell that the stone exhibits fluorescence. For example, when looking at a fluorescent diamond that is J color or lower, strong fluorescence may make the stone appear whiter when compared to a non-fluorescing diamond. It may also have the opposite effect on a high color diamond; D color may appear to have a blueness or cloudy appearance. Fluorescence currently has a negative effect on the value of the diamond; strong fluorescence can reduce the value of a diamond by up to 25%.

Step 9: Analyzing The Metal

The jewelry item will be weighed in grams and then the weight of anything non-metal (such as diamonds or other gemstones) will be deducted from the initial weight. The metal will then be tested to determine what it is; some countries apply a Hallmark that will be stamped on the item guaranteeing what the metal is.

Testing the metal can be done by various methods. Touch acid testing involves scrapping a small amount of metal and then applying a small drop of acid, each acid will be an indicator to the metal type. The precious metal prices change daily and the price paid per gram will be the price on the day of valuation.

Our Offices

New York

535 5th Avenue, 11th Floor,
New York, New York
10017, USA


Berkeley Square House
Berkeley Square, Mayfair
London, W1J 6BD, UK


212 JQ Modern
120 Vyse Street, Hockley
Birmingham, B18 6NF, UK

535 5th Avenue, 11th Floor,
New York, New York
10017, USA

Berkeley Square House
Berkeley Square, Mayfair
London, W1J 6BD, UK

212 JQ Modern
120 Vyse Street, Hockley
Birmingham, B18 6NF, UK