Natural diamonds are precious gemstones formed deep within the Earth's mantle over millions of years. They are created under high pressure and temperature conditions, resulting in a crystalline structure made of carbon atoms. Natural diamonds are often found in volcanic pipes and alluvial deposits, and they come in various colors, including colorless, yellow, and blue. These gemstones are highly valued for their brilliance and durability, making them popular choices for jewelry, especially in engagement rings. The Gemological Institute of America (GIA) grades diamonds based on the Four Cs: cut, color, clarity, and carat weight, which help determine their quality and value.