Gemstones are minerals with regularly arranged atoms that make them suitable for jewelry. The qualities that determine a gemstone's desirability are brilliance, hardness, color dispersion, and refraction. The three cardinal virtues of a gem are beauty, durability, and rarity. Beauty is defined by the five C's - color, cut, clarity, carat, and certification. Durability depends on a stone's hardness, cleavage, brittleness, toughness, and resistance to heat, pressure, and chemicals. Rarity is influenced by availability, fashion trends, political/economic conditions, and phenomena associated with the stone.