The solid substance known for being very hard and valuable is diamond. Diamonds are made of carbon atoms arranged in a crystal structure, which gives them exceptional hardness, making them the hardest known natural material. Because of their hardness and brilliance, diamonds are highly sought after for use in jewelry and are also utilized in various industrial applications like cutting tools and abrasives. Their rarity and the intricate process of extraction and polishing further enhance their value. Diamonds are often associated with luxury and significant life events, such as engagements and weddings.