Opal Buying Guide

Step 4: Gem Grading

Lesson 18

Opal gemstones are evaluated a little differently than other gemstones. The International Gem Society opal price guide features a grading system and terms unique to opals. A full description of these differences can be found in our Premium article on Appraising Opals. For the benefit of those interested in opal buying, here is a brief explanation of these terms.

  • Opals have grades of below commercial, commercial, good, fine, and extra fine. These assessments cover an opal’s colors, directionality of flashes, imperfections, and cut.
  • Body tones, from N1 (black) to N9 (white), describe the base color of a stone, without play of color. This system is used to distinguish black, dark, light, and white opals. Stones from N1 to N4 are considered black opals. N5 to N6 are considered dark opals. N7 to N8 are considered light opals. An N9 is considered a white opal.

Opal Buying And The 4 Cs

Opals can still be evaluated in terms of color, clarity, cut, and carat. However, you’ll find opals have some additional conditions that must be taken into account to properly judge their value.


Color is the most import factor …

Premium Article

This is a Premium Article. Please become a member to read this entire article and gain access to hundreds more like it.

Membership options

Full Article Details

Content Length 1826 words
Reading time 9 min 8 sec

Here's what you get if you unlock this article:

  • Opal Buying And The 4 Cs
    • Color
      • Number of Colors
      • Clarity of Colors
      • Brightness of Fire
      • Coverage
    • Clarity (Imperfections)
    • Cut
    • Carat
  • Opal Buying: Special Considerations
    • Directionality
    • Character
    • Patterns
    • The Opal's Face
    • Boulder and Matrix Opals
  • Opal Buying: Jewelry Considerations
    • Composite (Assembled) Opals
    • Treatments and Enhancements
    • Care

Plus, additional member-only benefits:

  • Exclusive access to other premium articles and courses
  • Unlimited access to our gem pricing guide
  • Participate in our member-only forums
Membership options