Gemas are precious or semi-precious stones that are often cut and polished for use in jewelry and decorative items. They are valued for their beauty, rarity, and durability. Common types of gemas include diamonds, rubies, sapphires, and emeralds, each with unique colors and characteristics. The formation of gemas occurs over millions of years through geological processes. They can be found in various locations around the world, with some regions known for specific types, such as Colombia for emeralds and Myanmar for rubies. Gemas are often graded based on factors like color, clarity, cut, and carat weight.