How to grade colored gemstones and diamonds including using the 4Cs --Color, Clarity, Cut, and Carat Weight.

Carats and Gemstone Grading

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.

clarity grading diamonds - brilliant round cut SI1
Clarity Grading Diamonds

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

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Clarity Grading for Colored Gemstones

Many factors contribute to a colored gemstone's clarity, and how you discuss it can affect your sales. Learn how gemologists conduct clarity grading tests.

white diamonds - ring set
Color Grading White Diamonds

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

grading colored diamonds - the Hope Diamond
Color Grading Fancy Colored Diamonds

Fancy colored diamonds require their own color grading standards. Learn the GIA and Argyle grading systems and how to find signs of artificial coloration.

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Traditional Diamond Cut Grading Methods

Traditional diamond cut grading methods prepare gemologists for making evaluations with minimal time, tools, and references. Learn the GIA and AGS systems.

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Modern Diamond Cut Grading Methods

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

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Distinguishing Diamonds: Educating Your Eyes

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

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Evaluating Gemstone Cutting: The Five Ps

Of the Four Cs of gem grading, only the cut is something a faceter can control. Learn how to evaluate gemstone cutting accurately with the Five Ps system.

gemstone grading - diamonds and colored gems
An Introduction to Gemstone Grading

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.

Grading Gem Carvings

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

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How to Grade Set Gemstones

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

Guide to GIA's Diamond Cut Grading System

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

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Advice for Determining Gemstone Value

Judging gemstone value is complex. New gemologists can have trouble with this. These four examples will show you how to identify the best gems.

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A Consumer's Guide to Gem Grading

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

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Choosing, Rating, and Grading Diamonds

First-time gem buyers may not understand how choosing, rating, and grading diamonds work. Our complete guide explains and offers advice on all three.

Common Sense Gemstone Grading - Subjective Terms
Common Sense Gemstone Grading: An Alternative System

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

cushion cut - grading fancy cut diamonds
How to Grade Fancy Cut Diamonds

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

Colored Stone Grading System

"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.

chrome tourmaline buying - fancy oval
Chrome Tourmaline Buying Guide

Our chrome tourmaline buying guide can help you learn how these gems are graded, what to avoid, and how to identify a high quality stone.

verdelite - pear cut
Green Tourmaline (Verdelite) Buying Guide

Our verdelite buying guide can help you learn how verdelites are graded, what to avoid, and how to identify a high quality stone or a bargain in the rough.

Indicolite - Brazil
Blue Tourmaline (Indicolite) Buying Guide

Our indicolite buying guide can help you learn how these blue tourmalines are graded, what to avoid, and how to identify a high quality stone.

rubellite buying guide - pendant
Rubellite Tourmaline Buying Guide

Our rubellite buying guide can help you learn how rubellites are graded, what to avoid, and how to identify a high quality stone or a bargain in the rough.

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Exposing Diamond Overgrading at EGL Labs

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

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FTC Guidelines for Grading Diamond Quality

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

modern cuts - Hanneman diamond cut grading system
An Introduction to the Hanneman Diamond Cut Grading System, Lesson One

Use the Hanneman diamond cut grading system to derive the cut grade of any round brilliant with minimal measurements and calculations. Learn more here.

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Cut Diamond Grade Categories: The Hanneman Diamond Cut Grading System, Lesson Three

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

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Basic Diamond Proportions: The Hanneman Diamond Cut Grading System, Lesson Two

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 them.

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Evaluating Diamond Cuts: The Hanneman Diamond Cut Grading System, Lesson Four

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

solitary diamond ring - FTC diamond jewelry updates
2018 Update to the FTC Diamond Jewelry Guides

The US Federal Trade Commission (FTC) can help jewelry marketers avoid making deceptive claims. Learn about the FTC diamond jewelry guide updates for 2018.