How to Grade Yellow Topaz

Weigh the gemstone carefully with a scale that shows carats. The higher the carats (and larger the stone as a result), the more expensive it will be. Use your own judgment as to whether or not a larger stone or a smaller one will be to your enjoyment, as everyone's budgets, personalities and personal tastes will vary widely. Know your market beforehand for yellow topaz. Example: if the current rate averages at $50/carat and someone wishes to sell you a 2-carat yellow topaz for $10, you'll know something is wrong.

Look at the cut of the gemstone. The cut is how the gemstone has been shaped to best effect. Determining a stone's cut is almost an art in itself. For nonprofessional gemologists, the cut is often the most difficult aspect to judge. Rough topaz of any color fresh from the mine tends to be elongated and prismatic. The resulting gemstone cuts are usually pears, cushions, elongated ovals and emerald cuts. (Blue topaz is an exception: You can produce it in any cut and style that exists). Cabochon-cut topaz is rare. If the cut is not symmetrical, or bulges strangely, from the normal topaz cuts, the grade will not be as high.

Use the magnifier to check the facets for smoothness and the crispness of the facet junctions. Compare it to other similar yellow topaz to see how the brilliance and sparkle looks. Make sure the windowing, or front facets, are to your taste and not detrimental to the cut of the gemstone. Cabochons do not require magnification; their cut is such that you can hold it out and let the play of light show you its imperfections.

Magnification is often used to find the clarity of the gemstone. Clarity is how many "inclusions" are within the gemstone itself. Inclusions are cracks, holes or even bits of minerals that interfere with the way light flows through the gem. One grade often used is "eye-clean," wherein the inclusions that exist cannot be seen by the naked eye. Most topaz is reasonably clean. Eye-visible inclusions bring down the price of the gemstone. To find inclusions in some gems, a magnifying lens of some type is required (though if you can't see them with the naked eye, most people are satisfied).

Look at the color of the topaz. Color is judged in three categories: hue, saturation and tone. Hue is the actual color of it: yellow. Saturation is whether it is strong or weak, like a pastel versus a "jewel-tone." Tone is how light or dark the gem is. Therefore, a strong, rich yellow topaz will be more expensive, and graded higher, than the yellow topaz that is just up from colorless. A yellow topaz that has a green tinge will not be as expensive as the purely yellow kind. Ask if the topaz has been irradiated or otherwise color-treated, as naturally occurring colors are more expensive (and rarer) than those produced by man.