As found in their natural state, any
no
Diamonds can be cut into almost any shape.
Three diamonds arranged in a line can form the shape of a triangle.
Octahedron
a cube
no
No, they are typically shaped like diamonds.
quadrilateral(squares,rectangles,diamonds,etc.)
you have two diamonds and a cross
Some raw diamonds appear to be pyramids, or a pair of pyramids joined at the base. The edges are not sharp and these descriptors only approximate the shape of the natural stone. You can follow the link, below, to learn more about raw diamonds.
No. Some diamonds have a 'classic' shape as raw stones, and they look like pyramids, or two pyramids joined at the base. But not all raw diamonds have this same shape. Cut and polished diamonds also have a variety of shapes. Diamond cutters plan and cut raw stones to highlight a stone's best clarity and colour qualities while preserving its highest carat weight.
"Mine Diamonds" or "Old Mine" Diamonds refers to a specific shape of a cut and polished diamond popular many years ago. Diamonds that are mined from the earth are in a "rough" state, that is not yet cut and polished. The rough diamond is then cleaved, or sawed into two or more pieces, and then those pieces are shaped by further cutting, bruting, or polishing into a specific shape. The popular shapes of diamonds today include the Round Brilliant (the most popular) the Princess, the Emerald, the Radiant, the Pear, the Marquise, the Oval, the Heart, the Cushion, the Trillion shapes. The "Old Mine" shape was the early predecessor of the Round Brilliant, and resembled the modern Cushion shape. The Old Mine shape evolved into the "Old European" shape, which was more round.