Grading Gemstones and Diamonds

The effects of the 2014 scandal over diamond overgrading at EGL labs are still emerging. Learn what gemologists and retailers can do to prevent…

Fancy cut diamonds can have any finished shape, except round. These stones have their own grading criteria, in particular regarding proportion…

Gems in jewelry settings can’t be evaluated the same way as loose stones. These guidelines are for gemologists learning to grade set gemstones.…

The US Federal Trade Commission (FTC) can help jewelry marketers avoid making deceptive claims. Learn about the FTC diamond jewelry guide updates…

Distinguishing diamonds from their lookalikes requires educated eyes. Learn what visual features to look for and the properties of many popular…

First-time gem buyers may find diamond grades confusing. Our consumer guide explains how diamonds are evaluated and gives advice on how to choose…

Learn how gemologists evaluate color, clarity, cut, and carat for gem grading. Consumers can use this information to find the right stone for their…

The FTC requires jewelers to accurately represent the diamond quality grading systems they use. Learn the guidelines and protect yourself from…

The Hanneman System makes evaluating diamond cuts easier. You can use total height and C/P ratios to cut grade round brilliants without subjective…

The Hanneman System simplifies cut diamond grade categories. Learn how to identify the worst cut stones quickly before taking unnecessary measurements.…

In the Hanneman cut grading system, you must consider diamond proportions to grade a round brilliant stone. Learn what they are and how to calculate…

With the Hanneman diamond cut grading system, you can derive the cut grade of any round brilliant with minimal measurements and calculations.…

The GIA modern diamond cut grading method is the most widely accepted in the industry. Our step-by-step guide covers the tools and techniques you’ll…

Traditional diamond cut grading methods prepare gemologists for making evaluations with minimal time, tools, and references. This step-by-step…

Mastering clarity grading diamonds takes a lot of experience. This grading guide, with definitions, images, and examples, can help beginning…

Mastering the art of color grading white diamonds is a challenge. Learn about the standards, terms, tools, and testing procedures and start practicing.…

The color grading standards for white diamonds don’t apply to fancy colored diamonds. Learn the GIA and Argyle grading systems and how to find signs…

Don’t underestimate the importance of clarity, one of the Four Cs of gemstone grading. For faceted gems, basic clarity grading involves evaluating…

Rare chrome tourmaline can show an emerald-like green color. With a highly desired color and tourmaline’s excellent jewelry stone qualities,…

Blue tourmalines or indicolites are a popular jewelry stone. However, some of these gems are often misrepresented.

Looking for a tourmaline jewelry stone? If you like green and you’re on a budget, green tourmaline or verdelite is the gem for you.

In recent decades, something remarkable invaded the thinking process of the colored stone industry. From dealers to consumers, they all discovered…

Like all tourmaline gemstones, rubellite wears well in almost any type of jewelry. This stone’s raspberry-like color draws a great deal of attention.…

Many new gemologists buy low-quality gems believing they’ve found a real bargain. However, judging gemstone value is very complex.

There were no standards for grading gems ’til the 30’s. Then the G.I.A. instituted the Four C’s method for diamonds, which has now become the standard.…

Can gem grading avoid subjective terms? Learn about gemologist Jeff Graham’s common sense gemstone grading system, an alternative to commercial…

Carats are the units used to measure gem weight and one of the main factors in gem grading. Learn what affects the value per carat of various gem species.…

Gem carvings are judged on material, workmanship, and artistry.  Learn how to apply these criteria to a piece with our step-by-step guide.

“Just Ask Jeff” shares his thoughts on the Color Stone Grading System of The GIA. In May 2008, he had been informed that the grading system was modified.…

This is an explanation of the GIA’s Diamond Cut Grading System complete with clear photographs demonstrating each of the grades.