An inclusion is an internal clarity characteristic formed naturally deep within the earth as a diamond crystallizes under intense heat and pressure. Ranging from tiny trapped mineral crystals to internal growth stress cracks, inclusions serve as unique natural “fingerprints” within the gemstone. Along with surface blemishes, inclusions directly determine a diamond’s clarity grade on standardized laboratory reports, serving as the horizontal axis on the Rapaport Price List.
Formation and Common Types of Inclusions
During the crystallization process billions of years ago, trace minerals or structural irregularities often became trapped inside the growing diamond lattice.
- Crystals and Pinpoints: Small mineral deposits embedded within the diamond. Pinpoints appear as tiny dots, while larger internal crystals can be mineral-colored or dark carbon spots.
- Feathers: Internal fractures or stress cracks within the crystal structure that often resemble delicate white feathers.
- Clouds: Clusters of microscopic pinpoints grouped together, which can sometimes create a localized hazy or milky appearance inside the stone.
- Needles and Knots: Long, thin mineral inclusions resembling fine rods, or included diamond crystals that extend to the outer surface of the polished stone.
Impact on Clarity Grading and Valuation
Inclusions are evaluated under standard 10x magnification by gemological laboratories such as the GIA to assign a clarity grade spanning from Flawless (FL) to Included (I1-I3).
- The Five Assessment Factors: Laboratory graders determine a diamond’s clarity grade based on the size, number, position, nature, and color/relief of its inclusions.
- Position and Relief: Inclusions located directly beneath the central table facet or those with dark contrast (high relief) have a greater impact on the clarity grade than small, light-colored inclusions hidden near the girdle.
- Eye-Clean Concept: In trade terminology, a diamond is considered “eye-clean” if its inclusions are invisible to the naked eye without magnification. Eye-clean stones in the VS2 and SI1 range offer substantial commercial value to trade buyers.
Inclusions on the Rapaport Price List
The Rapaport Price List uses clarity as one of its core valuation metrics to establish weekly benchmark price per carat grids.
- The Clarity Axis: Clarity grades form the horizontal columns on every Rapaport Diamond Price List matrix, ranging from IF (Internally Flawless) down to I3 (Included).
- Value Discount Spreads: As a diamond moves rightward across the Rap Sheet into lower clarity categories (such as SI2 or I1), its baseline price per carat drops significantly to account for higher inclusion visibility and potential structural risks.
Listing Requirements and Trade Practices
In inclusions and clarity assessment, market platforms prioritize strict accuracy, high-resolution imaging, and full disclosure.
- Vision360 Imaging on Rapaport Auctions: Single stones entered into Rapaport Auctions are scanned using advanced Vision360 imaging technology, allowing buyers to inspect every internal inclusion, feather, and cloud in high-resolution 360-degree detail before bidding.
- GIA Validation on Rapaport Trade: When listing diamonds on Rapaport Trade, inclusion plots and clarity characteristics uploaded by sellers are cross-checked against GIA database records to ensure exact report matching.
- Disclosure Standards: Full disclosure of significant inclusions is mandatory across trade channels, particularly for heavy feathers that could compromise structural integrity during setting or re-cutting.
- Blemish Distinction: Trade terminology distinguishes internal inclusions from external blemishes (such as surface scratches or polish lines), ensuring buyers evaluate structural purity and surface finishing independently.