Lonsdaleite

Lonsdaleite, also known as hexagonal diamond, is a rare and naturally occurring allotrope of carbon similar to traditional diamonds but with a hexagonal crystal structure instead of cubic. This distinctive structure gives lonsdaleite properties that can make it harder or more optically interesting than regular diamonds. It is typically formed under extreme conditions, such as meteorite impacts that exert immense pressure. Due to its unique atomic arrangement, lonsdaleite may have potential for advanced industrial applications, though it is less common and less studied than conventional diamonds.