If you found a Diamond you like, and it is not certified there is nothing wrong with asking your Jeweler to send it to a reputable independent Gemological Laboratory for certification. This request is a standard practice in the Diamond Industry. If you never heard of the Laboratory, don't feel shy about giving them a call to check them out. Also, if the laboratory is an independently owned franchise and the certificate you were given is not local, you may want to call up the lab, either the local one or the one that issued the certificate, and ask them by which standards they grade their Diamonds. Find out if they honour the grades given out by the other branches.
Every lab has a certificate number, which uniquely identifies a Diamond.
The Lab keeps an internal copy of everything which you see on the certificate, plus some additional information for their files. Size Matters Diamonds are weighed to the thousandth of a carat with a digital measuring device. On the certificate, weight is rounded to the hundredth of a carat. It's all Proportional Depth percent refers to the percent of the depth of the Diamond, table to culet, relative to the width of the stone. The Table of a Diamond refers to its largest facet, the main part of the Diamond you look at when the stone is face-up.