Gemstone Certification and Quality Grading: Diamonds vs. Colored Gemstones

Customers often ask why we don’t label tanzanite, sapphire, or other colored gemstones with clarity grades like VVS or VS, or with labels such as AAA+, the way diamonds are sometimes presented. The short answer is: VVS/VS is a diamond clarity terminology, and colored gemstones do not follow a single, universally standardized grading scale in official lab reporting.

This article explains the key differences between diamond grading and colored gemstone evaluation—plus the most common misconceptions in the market.

1) Why diamonds are graded differently from colored gemstones

Diamonds are highly standardized in gemology. The most widely recognized framework is the 4Cs:

• Carat (weight)
• Color – D to Z scale (for near-colorless diamonds)
• Clarity – FL, IF, VVS1/2, VS1/2, SI, I
• Cut

Terms like VVS, VS, SI are diamond clarity grades defined within diamond grading systems. Colored gemstones, however, have different typical inclusions, color phenomena, and value drivers—so the same approach cannot be applied 1:1.

Using VVS/VS for tanzanite or sapphire is therefore misleading.

2) How colored gemstones are evaluated (tanzanite, sapphire, ruby…)

For colored gemstones, there is no single universal grading scale comparable to diamond clarity grades. In practice, value and quality are judged more holistically, primarily based on:

• Color (hue, saturation, tone) – often the main price driver
• Clarity – always evaluated in the context of the gemstone species
• Cut (proportions, symmetry, overall appearance)
• Weight (ct)
• Treatments (e.g., heating, diffusion, impregnation—depending on the stone)
• Origin (if the lab can determine it)

Most reputable labs issue identification reports that describe measurable characteristics, treatments, and sometimes origin—rather than assigning marketing-style “tiers” like AAA+.

3) What “AAA / AAA+” means (and why it’s usually not a lab grade)

Labels such as AAA or AAA+ are typically seller-defined marketing terms, not standardized lab grades. In most cases they:

• have no universally defined criteria
• vary from one seller to another
• are not objectively comparable across the market

That’s why you generally won’t see a serious lab report stating “Blue Sapphire 3.00 ct – AAA+”. Labs focus on identification and documented facts, not promotional labels.

4) What a gemstone certificate actually confirms (and what it doesn’t)

A gemological report / certificate typically:

• confirms identity (species, natural vs. synthetic vs. imitation)
• lists basic data (weight, measurements, and descriptive observations per methodology)
• documents treatments (e.g., heated—when detectable)
• sometimes states origin (when determinable)

❗ A certificate does not set the price.
❗ A certificate does not automatically increase value.

Real value is driven by the gemstone itself—color, clarity in species context, cut, rarity, origin (when relevant), and market demand.

5) Myths vs. reality: practice over illusion

❌ Myths

• “AAA+ is an official lab-certified top grade.”
• “Without a certificate, a stone is automatically less valuable.”
• “A certificate automatically increases the price.”
• “Colored gemstones are graded like diamonds (VVS/VS).”

✅ Reality

• Colored gemstones do not have a universal VVS/VS clarity scale like diamonds.
• AAA/AAA+ is usually marketing, not a lab standard.
• Certificates primarily provide identification and transparency—not pricing.
• Value comes from quality and demand, not from a label.

Conclusion: transparency instead of marketing labels

At MINERALS-STONES®, we follow practical gemological standards. Diamond grading via the 4Cs (including clarity grades) is appropriate for diamonds. Colored gemstones should be assessed holistically—especially by color, cut, potential treatments, and overall quality within the context of the gemstone species.

https://minerals-stones.com/en/13-investment-gemstones-natural-cut-stones