Neka
There are lots of sites where you can get that information, or if time is limited or you don't want to do the reading and research, then hire a qualified independent expert to help you.
check out the following sites.
http:www.accurateappraisal.com
http://www.consumersgemlab.com
http://www.eightstar.com
http://www.whiteflash.com
http://www.niceice.com
http://www.superbcert.com
http://www.goodoldgold.com
http://www.usacerteddiamonds.com
Most of these sites have tutorials about learning.
Hope this helps
Rockdoc