Diamond Education Center A diamond's weight is one aspect of a diamonds value. The way a diamond is cut has an influence on its brilliance. Most diamonds appear white in Color, but not all diamonds are the same. Clarity measures how many or few flaws are found within a diamond. The cost of a diamond is determined by a few factors. Learn what they are. A diamond certificate is a document from an independent testing laboratory. Insure your diamond will remain as beautiful as the day you purchased it.