Understanding diamond terminology is essential—especially if you're new to the world of fine jewelry. Knowing the correct terms helps you communicate confidently, avoid misunderstandings, and make smarter purchasing decisions. Here’s a guide to the most important diamond terms every beginner should know.

“Water 100 Diamond” (D Color Diamond)

You may have heard the term “Water 100 Diamond,” which is commonly used in Thailand. This refers to a D Color diamond, the highest color grade on the international diamond color scale.

Diamonds in the D Color grade are:

• Completely colorless

• Exceptionally rare

• Free from any yellow or brown tint

• Highly brilliant and reflective

The term “water” traditionally refers to clarity and transparency, while “100” represents the highest possible grade. In modern international standards, this corresponds directly to Color Grade D.

Rough Diamond

A rough diamond is a natural diamond in its original form, freshly mined from the earth. It has not yet been cut, polished, or shaped.

Characteristics of rough diamonds:

• Uneven, irregular shape

• No polished surfaces

• Limited brilliance until cut

Rough diamonds are generally classified into three categories:

• Gem Quality (≈20%) – Clear enough for use in fine jewelry

• Near-Gem Quality – Slight color or inclusions, often used in mid-range jewelry

• Industrial Quality – Opaque or heavily included, typically used for industrial tools and abrasives

Loose Diamond (Loose Stone)

A loose diamond refers to a diamond that has already been cut and polished but has not yet been set into jewelry.

Key points:

• Fully finished and ready for setting

• Sold individually

• Allows buyers to inspect quality before mounting

Loose diamonds are often preferred by buyers who want to customize their own jewelry design.

Diamond Certificate (Diamond Grading Report)

A diamond certificate is an official grading report issued by an independent gemological laboratory. It verifies the authenticity and quality of the diamond.

Reputable grading laboratories include:

• GIA (Gemological Institute of America)

• HRD Antwerp

• IGI (International Gemological Institute)

A diamond certificate typically includes:

1. Report Information

• Report number

• Issue date

• Diamond shape

2. The 4Cs Quality Factors

• Carat – Weight of the diamond

• Color – Degree of colorlessness

• Clarity – Presence of internal or external flaws

• Cut – Quality of the diamond’s proportions and symmetry

3. Proportions and Measurements

• Depth percentage

• Table percentage

• Angles and dimensions

4. Clarity Plot

• Diagram showing inclusions (usually for diamonds over 1 carat)

A certificate provides transparency and protects buyers from fraud.

Diamond Simulants and Lab-Created Alternatives

Terms such as:

• CZ (Cubic Zirconia)

• Swiss Diamond

• Russian Diamond

• Lab-grown Diamond

These refer to diamond simulants or laboratory-created stones.

Important distinctions:

• Diamond simulants (like CZ):

  • Look similar to diamonds

  • Different chemical composition

  • Much more affordable

• Lab-grown diamonds:

  • Created in controlled laboratory environments

  • Same chemical and physical properties as natural diamonds

  • Typically lower cost than natural diamonds

These options are popular among buyers with different budget preferences.