Saturday, 15 October 2016

The basics of diamond color grading | Diamond color grades.

Understanding a diamond color grading.

The subject of diamond colors is a extremely deep and complex subject and takes highly skilled and experienced graders to master the complexity of color in a diamond.

How is the color of a diamond determined?

Firstly color can be divided into 3 main categories namely

  • Regular colors
  • Fancy Colors 
  • Treated Colors

How are regular colored diamonds graded?

Diamonds have a color grading system that refers to the absence of color rather than color itself. Internationally recognized diamond colors are measured on a scale using the alphabet starting at D which is totally colorless to Z (pale yellow or brown color). D, E and F’s fall into the colorless category while G- J are near colorless. K- M are faint yellows,  N-R is very light yellow, S-Z is light yellow and Z+ is used to describe fancy color diamonds. Brown diamonds darker than the K color rage is usually described using their letter grade plus a descriptive phrase, for example, M - Faint Brown (Color Scale +Color description). Diamonds with more depth than the color Z will fall into the fancy color range.

n order to determine a color of a diamond, diamond graders compare a diamond against the set of master stones. Each master stone falls into a very narrow color category. 

What is important to note is that every grade of color falls into a different price range.

How are diamonds graded by a diamond grader?

Color grading of diamonds is done in a consistent and controlled environment or lighting box, fitted with daylight equivalent lamps (5500 -6500 degrees Kelvin). The reason for this is that the lower the lights degrees the more likely it will influence the color of a diamond.

Diamond grading lamps are between 5500-6500 degrees Kelvin

Accurate color grading can only be performed with unset diamonds. Natural color diamonds is graded from a side view (pavilion side view) unlike fancy colored diamonds that is graded from a top view (table side facing up).
diamond color grading, grading diamond colors
Normal diamond colors are graded from a side-view

 Why in-house grading is not as accurate as Laboratory color graded diamonds?

A laboratory will possess a complete set of master stones representing every color grade, the independent grader usually works with a smaller subset of master stones that covers only the typical grade range of color they expect to encounter while grading. A common subset of master stones would consist of mainly five diamonds in several increments for example D, H, L, P and Z. All other intermediate grades are estimated by the grader.

diamond color grading, diamond colors, fancy color diamonds
In-House graders only use a sub-set of master stones

How are Fancy Color Diamonds graded?

Diamonds come in a large variety of colors and any diamond exhibiting a color or

Yellow or brown color diamonds more intense in color than the color "Z” is considered a Fancy Colored Diamond

Fancy Color diamonds are graded using 3 main factors

  1. Hue
  2. Saturation
  3. Tone

1 Hue

Hue refers to the diamonds color classification for example; yellow, red, blue, brown etc.

There are 8 primary hues used in the fancy color range

  1.    Red,
  2.    Pink (
  3.   Orange,
  4.   Yellow
  5.   Green,
  6.   Blue,
  7.   Violet, 
  8.   Purple.

Although the primary color is used to describe the diamonds hue other colors are often combined with the primary hue to add a more detailed description for example; Yellow – brownish (primary hue + more detailed description). Two or more colors can be used alongside the primary hue. Brown and grey can be added as primary hues but are mostly used in combination with the other hues.

Laboratories use a list of 27 detailed hues to further describe a diamonds color.

  1. Red
  2. Orangy Pink
  3. Pinkish orange
  4. Orange
  5. Yellowish Orange
  6. Yellow-Orange
  7. Orange-Yellow
  8. Orangish-Yellow
  9. Yellow
  10. Greenish-Yellow
  11. Green Yellow
  12. Yellow Green
  13. Yellowish Green
  14. Green
  15. Bluish Green
  16. Blue Green
  17. Green Blue
  18. Greenish Blue
  19. Blue
  20. Violetish Blue
  21. Blueish Violet
  22. Violet
  23. Purple
  24. Pinkish Purple
  25. Pink Purple
  26. Purple Pink
  27.  Purplish Pink

At times modified color combinations can be added e.g., Brown overtone, Brown-Olive.

2. Diamond Color Saturation

Saturation refers to the intensity of the hue in the diamond and are classified in 9-10 classes. Some might add the Vivid+ while others may not.

  1. Faint
  2. Very Light,
  3. Light,
  4. Fancy Light,
  5. Fancy,
  6. Fancy Dark,
  7. Fancy Intense,
  8. Fancy Deep,
  9. Fancy Vivid or
  10. Vivid+

Diamond saturation | Diamond hue | Diamonds tone
Strong saturation in a diamond adds value to the diamond


Grading Fancy Pink Diamonds

Numbers are also used to describe diamonds saturation. Argyle diamonds in Australia will use the numbers 1-9 to describe the saturation of their Pink Diamonds. The number 9 is used to describe the Faint colors while the 1 is used to describe the vivid colors.

An example of Argyle’s number descriptions for their Pink diamonds would be -

1 P for a Vivid Pink or 1PP for a Vivid Purplish Pink etc.

Other Color terms used to grade the color of a diamond.

It’s not uncommon to find other terms referring to a diamonds color, especially the retail industry one would find "Champagne", "Cognac" and "Coffee" referring to different types of brown diamonds. The term champagne is often used to describe a light yellowish brown color. Cognac for a Orange-Brown diamond and Coffee for a diamond that is a Deep Brown or a Brown Vivid+ color diamond.

Some grading agencies may also describe brown stones as using the term “Fancy” in front of the description for example Fancy Yellowish-Brown, Fancy Light Brown, Fancy Intense Brown etc.


The tone of a diamond refers to the lightness or darkness of the primary hue.

How are diamonds Color treated?

Generally there are four major methods to artificially alter the color of a diamond: irradiation with high-energy subatomic particles; the application of thin films or coatings; and the combined application of high pressure and high temperature (HPHT). However, there is recent evidence that fracture filling is not only used to improve clarity, but can be effective in enhancing a diamonds color.

Irradiation and coatings only modify color (as some irradiation methods only produce a thin "skin" of color), and are usually only they are applied to polished diamonds but have been found on rough diamonds as well. HPHT treatment is used to modify and remove color from either rough or cut diamonds however not all diamonds are suitable for HTHP treatment. Irradiation and HPHT treatments are usually permanent.  Pressures of up to 70,000 atmospheres and temperatures of up to 2,000 °C (3,632 °F) are used in HPHT procedure.
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Saturday, 1 October 2016

Diamond viewing lamps | What is the best light / lamps for diamonds?

What is the best light / lamps for viewing diamonds?

There seems to be many options when it comes to lighting for diamonds. You find desk-lamps, lamps magnifiers on, small lamps, big lamps, some with 2 bulbs, some with 3 bulbs, some have different bulbs...  There are the cheap no-name brands, the in-between's and the more expensive brands that people trust and pay a arm and a leg for - simply because its recommenced or available by jewelry tool companies who we trust. The truth is most people wont be able to tell you the real difference between a excellent lamp and a poor lamp or why exactly they sell or use it.
diamond lamps, diamond cutting lighting, diamond lights, diamond polishing lamps
Commonly used desk lamp for viewing diamonds

Different lamps  / lighting for the diamond industry.

When it comes to lighting for diamonds you should know exactly where and for what the lighting will be used for as there are different uses for different lamps in the diamonds industry for example;

General diamond dealing lamps / lighting
Diamond cutting factory lighting
Rough Evaluation lighting
Diamond grading lighting
Jewelry evaluation lamps
Jewelry sales lamps and the list goes on and on.
Our blogs focuses more around the diamond cutting aspect and therefore we wont delve into the jewelry side of lighting to much. However there is a fantastic article in our further reading section at the bottom of this blog.

General lighting and lamps for diamond viewing.

The good news is that the most expensive lamps are not always the best lamps. The secret to excellent lighting is more in the light bulbs itself rather than in the lamp brand. The most excepted view for lighting in the diamond industry is a well balanced (they flicker or fade to a side) white daylight fluorescent light bulb (LED Light Bulbs).
(Not to be confused with Ultra Violet light measuring florescence in a diamond)
Fluorescent bulbs have a even, defused light that is excellent for consistent results.  
According to Verena Pagel-Theisen (Diamond Grading ABC pg 80) the color temperature of the light should have a value of 5500 degrees Kelvin for diamonds in the blue-white range and 6500 degrees Kelvin for colored diamonds.

diamond lights, diamond lamps, best lamps for diamonds, diamond grading lamps
White daylight fluorescent light LED bulbs

Why does the bulb need to be between 5500 - 6500 Kelvin?

The answer is; That the 5500-6500 range is similar to clear daylight conditions - typical clear noon day sunlight. Its easy to see why the lower temperatures will influence the color of the diamond.
The best range light bulbs for diamonds is between 5500 -6500 degrees Kelvin

We can further define the light into the following categories

  • Warm White: typically from 2600 Kelvin to 3500 Kelvin
  • Natural White: typically from 4000 Kelvin to 4500 Kelvin
  • Daylight White: typically from 5000 Kelvin to 5500 Kelvin
  • Commercial or Cool White: typically above 6000 Kelvin

Environment consistency is key to for viewing your diamonds.

Consistency in critical when it comes to diamonds and therefore a standardized, balanced and consistent lighting and viewing environment is necessary when viewing your diamonds. Even surrounding colors or objects can influence your view on a diamond. I have personally photographed and viewed diamonds where I had to remove strong colored objects in close proximity as it effected the diamonds overall diamond color. The best background  / wall colors remain dull white or light grays while using a diamond grading paper (also known as a diamond boat). The diamond boat is made of non-reflective paper and helps with consistency when checking your diamonds for color. Never overuse a diamond boat as it gets dirty pretty quickly especially in larger factories where it is used often.
Diamond boats are excellent for polished as well as rough diamonds

diamond grading paper | diamond boat | diamond cutting lighting, diamond lamps
Diamond grading paper (also know as a diamond boat)
GIA DiamondDockTM
G.I.A sells a viewing box called a diamond dock that is specially designed to provide a consistent viewing environment. You can read more on the the DiamondDock on OGI Systems website.

Diamond lighting, diamond lamps, lamps for viewing, diamond polishing
GIA DiamondDockTM
Diamond polishing, qaulity control in diamonds, diamond cutters, Conrad Kruger
Using the Diamond Dock

Diamond Factory lighting 

A diamond cutting factory is usually well lit with similar florescence light bulbs - this is further proof that the Name Brand Lamp is not as important as the light bulbs itself. Larger factories have several rows of lights above their diamond cutters to ensure that the cutters can focus, with relative ease, on very small facets, polishing lines and symmetry.
Image result for diamond cutting factory
Well lit diamond factory

Master Diamond cutters in smaller diamond cutting factories will still have a well lit factory as they are more involved with the color, clarity, cut, symmetry and polish of a diamond.

Diamond polish grading lighting

Once a diamond is completely polished in the factory it will go for quality control where the diamond is checked for polish, symmetry and cut. This is usually done with a microscope. All decent microscopes have decent build-in lighting. Desk lamps are added to the quality control area and they are switched on or of as to not interfere with the quality controllers microscope - as a darkfield illumination is often used by quality controllers. Notice the dull greys on the walls.

Diamond lighting, diamond lamps, diamond polishing, diamond cutting, Conrad Kruger
Quality Control of a diamond done by Microscope 

Further reading 

Displaying jewelry in the best light

All rights reserved 2016

Review of Diamond loupes | Diamond Cutting loupes

How to choose a excellent loupe for diamonds

There seems to be so many different loupes on the market that its becoming a challenge to choose a great loupe in the diamond and jewelry industry. Some loupes are pretty cheap while others simply rely on a specific brand name within the industry. We buy loupes at tool stores or diamond and jewelry shows simply because they are easily available but are these loupes really up to standard in the diamond and jewelry trade?

Although loupes come in various magnifications 6X, 8X, 10X, 14X, 20X etc. and with different lenses,  single, double and triple. The ideal loupe for diamond viewing is a 10X Triplet loupe.
Not all loupes advertised as "Triplet Loupes" are real triplet loupes - on closer inspection one would find only a single or double lens instead of the 3 lenses (Triplet Loupe). Its highly advisable to steer clear of cheap, no name brand loupes and as a diamond or jewelry professional you should at least own a decent loupe - not expensive but a decent loupe.

Why must a ideal loupe be a 10X Triplet loupe?

A triplet loupe has 3 lenses that consist of
  1. Magnifier 
  2. Color corrector (corrects color distortions)
  3.  Linear corrector (corrects linear distortions)
And is available with diameters ranging from  Between 15 - 21mm (Actual viewing area slightly smaller)
Its easy to see the advantages of a 10X Triplet loupe over the single or double lens loupes. There are thicker single lens loupes called Coddington Lenses identified by its thickness and special groove around the circumference that are supposedly as good as the Triplet Loupes - unfortunately I don't have enough data to comment on these loupes.

Why not use stronger loupes 14X, or 20X instead of the Triplet Loupe?

Firstly the standards set for ideal cut polishing by laboratories is graded within the 10X magnifying range (with a few shady terms and conditions - not similar to diamond cutting, or office conditions). Secondly the stronger the magnification the smaller the lens which has a negative effect on  light and limits your actual viewing area.

What brands are excellent 10X Triplet loupes?

The best two brands on the market is BelOMO (not a typo) and HastingsTriplets (Edmund Optics)
I prefer the BelOMO simply because it well priced and "Hasting Lenses" seem to vary in quality according to Hastings Triplets Edmund Optics themselves.

Review of the BelOMO Loupe

diamond loupe, diamond cutting loupe, diamond polishing loupe
BelOMO Loupe
BelOMO is well priced at around $30 and offers a 10X, Triplet loupe (21mm - 17mm viewing area) that has three lenses -
  1. achromatic, (denoting lenses that transmit light without separating it into constituent colors)
  2. color correction, 
  3. anti-reflection
This makes it possible to see the image as precise and clear as in the original with excellent depth and field ratio.  

According to the Loupe Store
Chromatic aberration is caused by a lens having a different refractive index for different wavelengths of light (lens dispersion), meaning that different colors focus at different distances from the lens. Longitudinal and lateral chromatic aberration of a lens can be seen as "fringes" of color around the image.  

Diamond loupes, diamond cutting loupe, diamond dealers loupe
Chromatic Aberration
 Chromatic aberration of a single lens causes different wavelengths of light to have differing focal lengths

Best diamond loupes, diamond cutting, diamond polishing, loupe for diamonds
Achromatic doublet
Chromatic aberration can be minimized by using an Achromatic Lens or Achromat.

Diamond cutting loupes, diamond polishing, diamond loupes, rough diamond loupes
Minimizing chromatic aberration

 Belorussian Optical and Mechanical Association (BelOMA), are also makers of sights for guided weaponry, camera lenses, and other optical components.

The BelOMO is also great for viewing,
  • Diamonds 
  • Settings of diamonds
  • Completed Jewelry
  • Antique Jewelry
  • Viewing castings (Jewelry Castings)
  • Precious metals ( Gold, platinum, silver rings etc.)
  • Semi- precious stones 
  • Precious stones 
  • Banknotes
  • Coins 
  • Machining  
  • Engraving 
Amazon Reviews on the BelOMO

Review of the Hastings Triplet loupe ( Edmund Optics)

Double the price of the BelOMO starting at $75 but a quality brand if bought from Edmund Optics.

Edmund Optics Hastings Triplets offer their unique three-element design provides 
  1. distortion-free, 
  2. color-correct viewing. 
The lenses in this series are computer-designed to interact with each other, contributing to the reduction or elimination of “pincushion” (a form of optical distortion in which straight lines along the edge of a screen or a lens bulge toward the center) distortion and chromatic and spherical aberrations. The triple lens system is made up of two concave meniscus elements cemented to a double convex lens. Unlike many inferior “Hastings” on the market, Edmund Optic Hasting triplets are centered and edged, an expensive process, but one necessary to achieve maximum performance. 

The Edmund Hastings is also great for 

Jewelers, gemologists, engravers, machinists and manufacturers.

All rights reserved 2016 Conrad Kruger

Sunday, 25 September 2016

What are Melee diamonds? | Understanding Melee diamonds

What are Melee diamonds?

Melee diamonds is a term used for small diamonds usually diamonds that fall under the 0.18 carat range.
However since shipping, grading and diamond cutting costs escalated its not uncommon to find the range of Melee diamonds weighing up to 0.30.

How are Round Melee diamonds sorted?

Sorting and grading of melee diamonds can be a tedious process. Melee is sorted by category in;
  • Round Brilliants
  • Round 8 sided
  • Fancy Shapes
  • Color (White and Yellow)
  • Clarity (IF, VVS, VS, SI, and I’s)
  • Matching pairs
  • Sizes

Round Melee is sorted though the use of a diamond sieve. The diamond sieve has different size holes in them to allow the lager diamonds to be sorted from the smaller diamonds. 
melee diamonds, diamond sieve, small diamonds, diamond cutting, diamond polishing
Diamond sieve

Once these melee diamonds are sieved and sorted in similar sizes, they need to be graded. Melee diamonds need to be sorted, graded, matched and paired together in groups. Melee can also be sorted using a digital caliper. The digital caliper is useful for both Fancy Shape and Round Melee.

Melee diamonds, small diamonds, diamond chips, diamond cutting diamond polishing
Digital caliper

Round Melee Diamonds approximate mm to weight

1.        0.001 carat – 0.78 mm – 0.99 mm
2.        0.005 carat – 1.00 mm – 1.15 mm
3.        0.0075 carat = 1.16 mm – 1.23 mm
4.        0.01 carat = 1.24 mm – 1.40 mm
5.        0.02 carat = 1.56 mm – 1.80 mm
6.        0.025 carat = 1.81 mm – 1.88 mm
7.        0.03 carat = 1.89 mm – 2.10 mm
8.        0.04 carat = 2.10 mm – 2.33 mm
9.        0.05 carat = 2.24 mm – 2.43 mm
10.      0.06 carat = 2.44 mm – 2.50 mm
11.      0.07 carat = 2.51 mm – 2.73 mm
12.      0.08 carat = 2.74 mm – 2.80 mm
13.      0.10 carat = 2.81 mm – 3.10 mm
14.      0.12 carat = 3.11 mm – 3.23 mm
15.      0.15 carat = 3.23 mm – 3.54 mm
16.      0.18 carat = 3.55 mm – 3.83 mm

How are Melee diamonds graded?

Melee diamonds are graded in-house and not graded in a laboratory like larger diamonds as the costs are simply to high. Unlike larger diamonds Melee diamonds are graded in larger categories for color and clarity for example; White and Yellow and in clarity for example SI - Its not usually graded separately SI1, SI2 etc. However this can vary from company to company.

What are Melee diamonds used for?

It may seem like a waste of time to sieve and grade though large number of small diamonds. Individually they don't cost much but in larger quantities their overall value begins to add up considerably. Custom made jewelry often requires larger amounts of Melee. You will hardly find a wedding set that does not have some Melee on the sides to complement or complete a stunning setting. Melee is usually sold by carat weight and this is where the sorting and sieving pays of as a carat of Melee can start around $100 per carat to $3000+ per carat depending on the sizes, cut (Fancy or Round) and colors (White, Yellow or fancy colors).

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