From the Gemologist: More about Clarity

How a Clarity Grade is Assigned

When a trained diamond grader is evaluating a diamond for its clarity, he or she will view the stone with the naked eye and with 10x magnification to assess the overall impact of the diamond's clarity characteristics.  External characteristics do not affect the clarity grade below Internally Flawless (IF).  They will, however, factor into the polish grade.  There are many types of internal characteristics, but here is an brief explanation of the most common ones you will see:

  • Crystal - A foreign crystal trapped inside the diamond during the growth process
  • Feather - A break inside the diamond that is caused by blunt force or pressure applied to the stone
  • Pinpoint - A tiny crystal that appears literally no larger than a pinpoint when viewed at 10x magnification
  • Cloud - A series of pinpoints grouped together
  • Needle - An included crystal shaped like a rod
  • Indented Natural - A portion of the skin of the rough diamond crystal that falls below the polished surface of the diamond

After identifying all of the inclusions visible under 10x magnification, the grader then assesses the overall impact of the internal characteristic(s) based on five factors:

  • Size - How small or large is/are the inclusion(s)?
  • Number - How many inclusions are inside the diamond?
  • Position - Where are the inclusions located?
  • Nature - What type of inclusion(s) is/are present?
  • Relief - What is the visual impact of the inclusion(s)?

Once the diamond grader has identified the internal characteristics and assessed their impact on the diamond, he or she determines a clarity grade based on established guidelines set forth by the laboratory.

Reading Clarity on the Certificate

On the grading report for a loose diamond, you will see a single clarity grade assigned to the stone ranging from FL to I3 on the GIA scale.  Some labs such as AGS use their own nomenclature.  In addition to the clarity grade, the grading reports for most stones above one carat with be accompanied by a "diamond plot," or a map of the external and internal characteristics of the diamond.  Inclusions (most properly referred to as "internal characteristics") are found inside the diamond and are marked in red on all major laboratory reports such as GIA, AGS, and EGL.  Blemishes (or "external characteristics") are found on the surface of the diamond.  Blemishes are only noted on a grading report if the diamond is graded Flawless (FL) or Internally Flawless (FL), and they will be marked in green.

How/Why Clarity Matters

While given the choice, most women would probably want a Flawless diamond, a very high clarity grade is not needed for a diamond to be free of visible characteristics that may detract from the beauty of the stone.  Most people cannot see an inclusion with their naked eye until the diamond reaches the SI or I range.  That being said, one can still find a diamond that is essentially "eye clean" at SI1 if the stone is selected properly and by a knowledgeable diamond buyer.  For a diamond to be brilliant, it must return as much light as possible that enters the stone back to the eye.  Inclusions can interrupt the path of light and result in dull, lifeless stones regardless of the precision of the cut.  Inclusions can dramatically affect the durability of the diamond depending on their size, type, and location.  For example, a feather reaching the girdle of a diamond leaves the stone prone to chipping during the setting process or normal wear.  Keep this in mind when considering diamonds in the I range.

To select an eye clean diamond, I recommend purchasing diamonds that are grades VS2 (or perhaps SI1 if well-selected) or higher.  This way you can maximize the other three C's and get the most out of your budget.

Originally posted by me to on 4/5/2010.

The Truth about “Carbon Spots” in Diamonds

The Myth

Walk into any jewelry store, and ask to see a diamond with eye-visible black spots.  Ask the salesperson what the spots are, and he or she is likely to tell you that they are "carbon spots," or bits of carbon, the element that makes up a diamond, that were not dissolved when the diamond was formed.  Mother Nature was boiling up some carbon to form diamonds, and some of the carbon just didn't become a diamond.  It makes sense, right?  Wrong (well, mostly wrong).

The Truth

Diamonds can have inclusions of graphite, which is carbon that formed with a different atomic structure than a diamond.  Graphite is usually a dark gray color and can definitely appear black in various lighting conditions.  But not all inclusions are created equal.  There are many different possibilities as to what a particular inclusion can actually be.  The only quick answer is that dark inclusions are included crystals (xenocrysts) that may actually be a very dark-toned red, green, brown, etc.  The only way to know for sure is to have an advanced gemological laboratory use sophisticated equipment to analyze the chemical make-up of the inclusion.

The Moral

The moral of the story is this: if you are being sold a diamond that has "carbon spots," I recommend that you run away - far, far away - and find a more knowledgeable jeweler or gemologist.  And trust me, you do not need to dip into the I-clarity range to find a diamond that maximizes your diamond budget.

Originally posted by me to on 4/6/2010.

Clarity Enhancements: The Why and How

Why Clarity Enhance a Diamond?

Clarity-enhanced diamonds are interesting creatures in the diamond industry.  Some jewelers love to offer them as an affordable alternative to paying for a higher clarity grade, and others won't touch them with a 10-foot pole.  The most important point to remember about clarity enhancement is that it does not improve the clarity grade of the stone.  This might seem silly at first.  If the big black inclusions have been dissolved away or bleached out, why shouldn't the clarity grade go up?  The answer is that clarity enhancements are not natural and are not accepted as a normal part of the diamond finishing process.  They only improve the apparent clarity, or what the diamond looks like to the eye after the enhancements have been carried out.  A reputable gemological laboratory will grade the clarity of a clarity-enhanced diamond as if the inclusions were in their original state.  Ironically, these enhancements can actually worsen the clarity grade!  The purpose of clarity enhancement is to make the diamond more saleable to the consumer.  A jeweler can purchase a lower clarity diamond at a much more substantial discount than if purchasing higher clarity stones.  He or she then decides to have the diamond clarity enhanced with the ultimate aim or reaping a larger profit margin.

How Diamonds are Clarity-Enhanced

There are two main ways of enhancing the apparent clarity of a diamond: laser drilling and fracture filling.  These treatments may be appear separately or together in the same diamond.  Each method targets specific inclusions, and they are not a cure-all for included diamonds.

  • Laser Drilling - Diamonds are laser drilled in order to improve the appearance of dark, included crystals or staining caused by iron oxide.  An infared laser beam is aimed precisely at the inclusion, and it burns a microscopic hole (less than 0.2 mm wide) from the surface to the inclusion.  The heat of the laser can sometimes destroy the inclusion enough that no further treatment is necessary.  If not, the diamond is submerged in sulfuric acid dissolve the inclusion or to lighten the color of the inclusion.  Diamonds can actually have other diamonds in them as inclusions, and these cannot be removed because of diamond's immunity to sulfuric acid.  The laser leaves behind a permanent reminder of the treatment: a laser drill hole (LDH).  Laser drill holes become clarity characteristics that are taken into account when determining the clarity grade.  They are also noted on the diamond's plot.  The laser drill hole looks like a tiny tube extending into the diamond from the surface (not to be confused with a naturally-occurring growth tube).  To fill the hollow void left my the laster drilling, they might also be fracture-filled.  Laser drilling must be disclosed to the consumer.  GIA will grade laser-drilled diamonds so long as the laser drill holes have not been glass-filled.
  • Fracture Filling - Naturally-occurring breaks within a diamond can produce a white, feather-like inclusion that detracts from the beauty of the diamond.  To improve the look of these fractures, a special type of glass filling may be injected into the fractures.  The glass filling will ideally make the fractures more transparent and less noticeable.  If the fracture breaks the diamond's surface, the glass can be injected directly into it.  If the fracture is internal, a laser may be used to drill to fracture.  Laser drill holes themselves may be fracture-filled to diminish their appearance.  Fracture filling (and the accompanying laser drilling, if used) must be disclosed to the consumer.  Fracture filling is not considered a permanent treatment, as the glass come out of the diamond during normal wear, cleaning, or jewelry repairs.  Special care is required for fracture-filled diamonds.  Important: GIA will not grade fracture-filled diamonds.  This means that diamonds that are glass-filled to minimize the appearance of laser drill holes are ineligible for grading by GIA.  This is because it is not possible to accurately assess the pre-treatment clarity of the diamond.

Care and Disclosure

All diamond treatments must be disclosed to the consumer at every step of the sales process.  Diamond treatments such as fracture filling require special care and handling considerations.  These should be told to you by the jeweler.  The market for treated diamonds remains small compared to that of natural diamonds, so resaleability will be negatively affected.

Originally posted by me to on 4/6/2010.

Fluorescence and Diamonds: A Love-Hate Relationship

What Is Fluorescence?

In short, fluorescence is the emission of visible light when a diamond is exposed to X-rays or ultraviolet (UV) radiation.  Roughly one third of all diamonds fluoresce to some degree.  Under the GIA grading system, diamonds are viewed in a special UV light box under long-wave UV light to assess the color and intensity of a diamond's fluorescence.  Then, one of five grades is assigned to the diamond:

  • None
  • Faint
  • Medium
  • Strong
  • Very Strong

Just like the GIA color grades, fluorescence grades encompass a range of intensities.  To prove this point, many people can notice very faint fluorescence in diamonds with a GIA grade of "None."  Besides assigning a grade commensurate with the intensity of the diamond's fluorescence, diamond graders also note the color that the diamond fluoresces.  The overwhelming majority of diamonds that fluoresce (97% in one GIA study) emit blue fluorescence.  Rarely one can find a diamond with yellow, white, or orange fluorescence.

The Effect of Fluorescence

Fluorescence is a difficult concept for many jewelry professionals to understand and explain to their clients.  Thus, the diamond industry has tended towards discounting diamonds with fluorescence grades above Medium.  Diamonds with higher fluorescence grades are more difficult to resell than those with a lower grade.  D, E, and F-color diamonds with no fluorescence command premium prices in the diamond market.  It is said that fluorescence can cause colorless diamonds to look hazy or milky in daylight, as ultraviolet radiation is present in normal daylight.  On the opposite side, blue fluorescence can improve the apparent color of a diamond with a color grade of J or below because it offsets the yellow tint of the stone.  In order to get the best value in a diamond, we recommend our clients purchase diamonds with fluorescence grades of None to Faint.

The Ugly Truth

To test the true affect of fluorescence on apparent diamond color, GIA performed an experiment where trained diamond graders, diamond industry professionals, and average consumers were shown diamonds of varying fluorescence.  The average consumers preferred diamonds that fluoresce over those that do not.  Even the trained diamond graders were mixed in their preferences of the diamonds.  Indeed, when GIA was developing its grading report, fluorescence was meant as an identifying characteristic and not as a grading factor.  GIA has determined that, at best, fluorescence has a "weak" impact (positive or negative) on the apparent color of a diamond.  But since the jewelry industry steadfastly maintains its own views on diamond fluorescence, those are the views that affect diamond value on the market.

Originally posted by me to on 4/6/2010.