Diamond Inclusions

Diamond inclusions are the internal flaws that are found within its crystalline surface. These flaws are created due to irregular crystallization of diamond during its formation process. Small crystals are trapped inside when diamond is forming, and sometimes these crystal growth can lead to irregularities in atomic structure of diamond.

Diamond Inclusions

Natural diamonds are not created in laboratory under controlled environment. Formation of a natural diamond takes millions of years under intense pressure and heat, approximately 100 miles beneath the earth’s surface.

So, it’s natural for most diamonds to have Flaws. This being a natural phenomenon, pattern of flaws in one diamond can never be same as of another diamond. This is something that gives diamond its unique identity, and it's is very similar to unique finger-print patterns in humans.

Therefore, it will not be wrong to say - inclusions are diamond’s fingerprints. Diamond inclusions also help in differentiating between natural diamond and synthetic diamond, because one of the flaws of synthetic diamond is that it’s too perfect and does not have any flaws.

Diamond inclusions are present in all natural varieties and has quite an effect on diamond clarity. Degree of influence on clarity depends on number, location, size and color of inclusions. Very few diamond inclusions are visible to naked eyes but can be viewed from 10X magnifying lens.

Effect of Diamond Inclusions

  • Brilliance – Diamond inclusions affect the stone's ability to scatter and transmit light as these flaws block the light passing through diamond. Thus, it reduces the brilliance of the stone.
  • Durability – Diamond inclusions decrease its resistance to fracture.
  • Beauty – Large diamond inclusions or inclusions with color, reduce the beauty.
  • Price – As the inclusions in diamond increases, its price decreases.

Types of Diamond Inclusions

Following are the examples of diamond inclusions or internal flaws in different categories:

Bearding

  • Stress hairline cracks extending from girdles surface into the stone. It occurs during diamond cutting and bruiting process.
  • Lightly bearded girdle don’t interfere with diamond’s brilliance, but when diamond is heavily bearded then it reduces its shine. At times diamond is re-cut or re-polished to improve its brilliance.

Cavity

  • Cavity means presence of large or deep opening in diamond.
  • It’s the space left when a surface reaching the crystal drops out, or when cutter removes the crystal inclusion close to diamonds surface.
  • It may be result of part of feather breaking away.

Chip

  • Should not be confused with "Diamond Chip" - the term used for very small diamonds.
  • When viewed through 10X magnifying lens, chip appears to be a shallow opening on the surface of diamond.
  • It generally has rounded outline and is usually found on girdle, culet or on facet edges.
  • It’s caused due to damage that occurs during cutting and polishing.

Crystal

Diamond Inclusion Crystal
  • It is a mineral crystal (most often other diamond) trapped in diamond.
  • A crystal can be of any size, color or colorless, and can be located anywhere in crystal.
  • With naked eye crystals look like white or black spots or tiny dots.
  • Black spots can be crystals or reflection of crystals.

Cloud

  • These are microscopic small crystals with dust-like appearance.
  • Crystals are too small to be distinguished individually, but cluster appears white or gray patch in diamond.
  • As long as these clouds are small and diffused, they impact the clarity only slightly; however if they are large and scattered, they do influence the transparency and brilliance of diamond, making the diamond appear undesirably white.
  • Some clouds impart hazy look, while some are dense and opaque.

Cleavage

  • Cleavage refers to cracks in diamonds that are usually straight lines and parallel to one of the diamond’s crystallographic planes (read hardness of diamond for more information), or cleavage plane.
  • Cleavage affects the durability of stone. Crack can expand under mechanical stress or while setting in jewelry. It leads to splitting of the stone when placed in high pressure grip of prongs.
  • Stones with cleavage should be avoided because when set in jewelry and exposed to daily wear and tear, it can break the diamond.

Feather

  • It resembles the shape of a feather, and is commonly used to refer any breakage in a diamond.
  • The appearance of feather depends on the viewing direction. It may appear shiny, transparent, white or glossy.
  • It affects durability of diamond, especially if it’s on girdle area.
  • It can expand under mechanical stress, leading to breaking of stone.

Fracture

  • Breakage in diamond which is not parallel to cleavage plane is called Fracture.
  • It can be of any shape and gives diamond the chipped look.
  • It is often filled to improve the clarity of diamond, such diamonds are called Fracture Filled diamonds.
  • GIA does not grade fracture-filled diamonds, as fracture filling is not a permanent treatment.

Twining Wisp

  • It’s an inclusion resulting from distortion of crystal during its formation process. Twining wisp is basically, various inclusions getting twisted together during growth of diamond.
  • Inclusions like pinpoints, clouds, crystals, needles, feathers may group together and form white strip inside the diamond.
  • It appears flat and ribbon-like, and can be viewed by 10X magnifying lens through center of diamond. These are commonly found in fancy colored diamonds.

Pinpoint

  • It’s the minute crystal inclusion (under 10X magnification) in form of tiny dot.
  • Pinpoint is the most common flaw found in diamond.
  • It is usually of white color, but at times they can be dark as well.
  • It has dot-like appearance and does not affect the clarity of diamond.
  • It’s generally not mentioned on the plotting diagram of diamond reports and mentioned only in comment section.

Needle

  • These are crystal inclusion in the form of long and thin needles.
  • A needle can be viewed by naked eye if it has some color or is of noticeable size. Else it can be viewed by 10X magnifying lens.
  • A needle can be bright, white or dark in appearance.

Knot

  • When an inclusion reaches the surface of diamond then it is called Knot.
  • Knots are formed after cutting and polishing of diamond.
  • At times, knots look like slightly raised areas on a facet of diamond. It can be seen under proper lighting and 10X magnifying lens.

Grain center/lines

  • It’s in the form of lines or in the form of small concentrated area.
  • These are not visible from all direction, i.e. grains may be visible from one direction, but if you change the direction of stone, it may not be detectable.
  • Grains can be white, dark or transparent in nature. It’s result of improper crystallization of diamond during formation process or improper polishing of diamond. These grains are difficult to remove without huge weight loss.
  • Grain lines are commonly seen in fancy colored diamonds - mostly in pink diamonds.

Indented Natural

Diamond Inclusion Indented Naturals
  • An indented natural is a portion of original rough diamond crystal that is left unpolished. It extends onto the crown or pavilion.
  • The original surface of diamond might have growth lines, which are triangular in shape. This shows that diamond has been cut by experienced cutter where he has retained as much original weight that was possible without compromising on quality of cut.
  • Cutter generally leaves the indented naturals on pavilion, as it dips behind the polished surface of diamond and is less noticeable. It’s not visible when set in jewelry.
  • Cutter can remove it but in doing so, weight and price of stone reduces.

Laser-Drilled Hole

  • Laser treatment is done on diamond to enhance its appearance by removing inclusions. It does not improve the clarity of diamond but increases the saleability of diamond by lighting the inclusions.
  • It involves different processes, like - burning or bleaching the inclusions, or by dissolving them in etching fluid like sulfuric acid and hydrofluoric acid, so that inclusions are less visible.
  • Special drilling system is used, and tiny tunnel as fine as hair is created by a laser beam. The tunnel extends from surface of the diamond to the dark included crystal. At times inclusion appears dark due to total internal reflection. Air penetrating through laser drill-hole lightens the tone of inclusion.
  • Another process is, insertion of acid into drill channel under high pressure. The acid bleaches, etches or dissolves the inclusion depending on the properties and chemical composition of inclusion.
  • Laser-drilled holes are also filled with highly refractive wax or synthetic resin and sealed on surface. Thus, drill-holes are less visible and it protects from dust penetration.
  • Since the laser-drilled holes are permanent, GIA grades laser-drilled diamonds. GIA mentions the drilling under comment section. Classification of diamond into particular category depends on appearance of drilled holes.
  • Though drill-holes enhance the appearance of inclusions, it also leads to artificial internal defects.

Fracture Filled

Before Fracture Filling (left) and After Fracture Filling (right)

  • Laser-drilled holes and surface-reaching cracks in cut diamonds are sometimes filled with highly refractive liquid under strong pressure and temperature of around 400 degree C. This treatment is called Fracture Filling, and was developed in 1987 by Mr. Zvi Yehuda from Israel.
  • The milky air-filled cracks are difficult to detect when filled with highly refractive liquid. This treatment leaves the flash effect on diamond, i.e. when you slowly move the filled diamond, the fine liquid film in the cracks changes color.
  • Heat generated during setting of diamond in jewelry can damage the filling. Filling may also get damaged while cutting or repairing of jewelry.
  • As this treatment is not permanent, and since its durability cannot be guaranteed, GIA does not grade fracture-filled diamonds.

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