The diamond, the birthstone of April, is the most coveted gemstone. A diamond is the hardest natural substance and is the only gemstone prized for its complete lack of color. While the classic white diamond is most oftenly seen, diamonds can be mined in many colors; yellow and brown being the most common. The rarest and most prized colored diamond is the brilliant blue diamond. The April birthstone, the diamond, due to its brilliance and fire has become the symbol of love.