Useful Information

http://www.diamondhelpers.com/ask/0018-whycertificates.shtml
http://www.gemsociety.org/
http://www.theassayoffice.com/

GEMSTONES
http://www.agta.org/
http://www.gemstone.org
http://www.jewelrymall.com
GOLD

http://www.gold.org/

DIAMONDS

http://www.adiamondisforever.com/buy/
http://www.gia.edu/

Canada Diamond

Diamond Info.org Diamond Guide: Carat Weight - Color - Clarity - Cut

JEWELRY (general)

Federal Trade Commission Brochures
http://www.ftc.gov/bcp/conline/pubs/alerts/jewelweb.htm
http://www.ftc.gov/bcp/conline/pubs/alerts/goldalrt.htm

Jewelry Central - The Jewelry Portal of the Web: Education, Information, Shopping.

PEARLS

http://www.pearlinfo.com/consumer/index.html

PLATINUM

http://www.preciousplatinum.com

MISCELLANEOUS

http://www.onlypunjab.com/

http://www.company-wizard.co.uk