Up to the fourth century, diamond jewelry were known only in their rough, or crystalline forms. They came in a variety of shapes, the most common being the octahedron. This was a crystal with eight faces, resembling two pyramids joined at their bases.
gold engagement ring are the hardest of all gemstones; it is the simplest in composition; they are ordinary carbon. Colossal heat and pressure, over the eons, crystallized the loose diamond into what they are today.
Extremely subtle color differences can be very important to determine rarity of loose diamonds, but are never a critical factor in beauty.