Gemological Institute of America (GIA)
A nonprofit organization that offers gemstone identification and buying advice to consumers and training to those in the jewelry trade. The GIA provides lab services to the jewelry industry.

JewelInfo4U
Informational site with articles by volunteer editors from the jewelry industry. Includes articles on gemstones, buying guides, help for men, and common questions.

American Gem Trade Association
The natural colored gemstone and cultured pearl source of information and ideas.

DiaInfo.com
Information to help make shoppers aware of simulated stones and of diamonds that might have received undisclosed treatments to improve their appearance.

YourGemologist.com
A reference library covering natural gemstones and minerals, synthetic and treated gems. Also offers resources for people who would like to pursue a career in gemology.