Learning Center

Grading Gemstones and Diamonds

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

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…

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.…

Modern Diamond Cut Grading Methods

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…

Clarity Grading Diamonds

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

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.…

Chrome Tourmaline Buying Guide

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

Rubellite Tourmaline Buying Guide

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.…

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.…

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.…

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.…