Calibrated Gemstones by MM Size for Jewelry by GemSelectFor example a 65 mm round diamond, sapphire and opal, all cut in the same proportions will all have different weights The diamond (with a specific gravity of 352,) will weigh 1 carat A sapphire (specific gravity 4,) will weigh 114 caratsQuartz Crystals (Xtal) SMD Type QuartzCom, Oscillators ,QuartzCom, Oscillators, Crystals and Filters ...