Diamond jewelry is a gift that she is guaranteed to love, but sometimes it can be difficult to know what exactly you are buying. Looking at diamonds with the naked eye will not help you judge its quality. Do not be afraid to ask a jeweler to use their jewelers' loupe (a magnifying device) and to explain the diamond to you. Gemologists use a diamond ranking system. By understanding this system, and what the letters mean, you can choose the perfect diamond. The "4 Cs" -- color, cut, clarity, and carat weight are the key factors in determining the price of diamond jewelry.