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Beyond the 4Cs of Diamond Buying | Key Factors that Impact Beauty and Value

Choosing a diamond involves understanding the 4Cs and considering other factors that greatly impact the beauty and value of a diamond. Beyond the 4Cs, diamonds with a milky appearance and/or a brown tint are crucial factors to consider when purchasing a diamond. These aspects are often overlooked but can significantly impact a diamond's appearance, regardless of high clarity and color grades. Even a D-Flawless diamond can appear dull and lifeless if it has a milky tone, detracting from its brilliance. These diamonds are commonly referred to as "BGM," "TLB," "Milky," and "Cloudy," among other terms. BGM stands for "Brown, Green, and/or Milky," while TLB denotes "Top Light Brown." In the diamond trade, such diamonds are sold at a loss or below market value, often at a significant discount.

  1. The Basics: The 4Cs of diamond buying:

    a. Cut: Refers to the symmetry, proportions, and overall craftsmanship of the diamond. The cut greatly impacts the diamond's brilliance, fire, and scintillation. It is graded from Poor to Excellent.

    b. Clarity: Measures the number and size of inclusions or blemishes within a diamond. Clarity grades range from Flawless (no inclusions or blemishes visible) to Included (inclusions and/or blemishes visible to the naked eye).

    c. Carat: Represents the weight or size of the diamond. One carat is equivalent to 0.2 grams or 200 milligrams.

    d. Color: Evaluates the presence of any hue in a white diamond. The color grading scale ranges from D (colorless) to Z (light yellow).

  2. Factors NOT mentioned on a diamond certificate but greatly impact Value and Appearance:

    a. Milkiness: A milky or cloudy appearance in a diamond caused by microscopic pinpoints scattered throughout its structure. These pinpoints are not considered clarity inclusions, but when concentrated, they can affect the overall appearance of the diamond. A trained eye, proper lighting, and clear master stones are needed to identify milkiness.



    b. Brown Tinge (BGM): BGM stands for "Brown, Green, and/or Milky" and refers to diamonds with a brown or green tint or those with a milky appearance. This factor can greatly impact a diamond's beauty and value, regardless of its clarity and color grades. Diamonds with these characteristics are usually sold at a discount, and this is mainly why you see diamonds graded the same but priced very differently as diamonds that have this nuance or defect are usually sold at a discount, mainly online to less discerning buyers.

Brown, green, or milky (BGM) tinges in diamonds can result from various factors related to the diamond's formation, trace elements, and lattice structure. Here are some of the primary causes of these tinges:
  • Formation and geological conditions: Diamonds are formed deep within the Earth's mantle, or under lab-grown conditions mimicking the earth's process under extreme pressure and heat. The specific geological conditions during the diamond's formation can cause the presence of impurities, which can, in turn, affect the diamond's color or transparency.
  • Trace elements: The presence of trace elements within the diamond's crystal structure can cause color tinges. For example, nitrogen impurities can cause a yellowish or brownish hue, while boron impurities can cause a bluish or greenish tint.
  • Lattice structure defects: Diamonds consist of carbon atoms arranged in a crystalline lattice structure. Sometimes, irregularities or defects occur in the lattice, which can lead to color tinges. For example, vacancies in the lattice or displaced carbon atoms can cause a brownish or greenish hue, while radiation damage can create green colors.
  • Plastic deformation: Diamonds can undergo plastic deformation due to the extreme pressure and temperature conditions they experience during their formation. This deformation can cause changes in the atomic structure, resulting in the appearance of brown, green, or other color tinges.
  • Graining: Graining refers to irregular growth patterns in the diamond's crystal structure. This can cause light to scatter differently within the diamond, potentially leading to a milky or hazy appearance.
  • Inclusions: Inclusions are internal or surface-reaching imperfections within the diamond. Inclusions made up of minerals or other materials can cause a milky or hazy appearance in a diamond. For example, clouds of tiny pinpoints or groups of included crystals can give a diamond a milky appearance.
It's essential to consider these factors when selecting a diamond, as they can impact its overall appearance, brilliance, and value. Always ensure you receive a grading report from a reputable gemological laboratory, and consult with a professional gemologist or jeweler when in doubt.
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