|A really poorly cut native stone. This is what I usually refer to as the "pineapple" cut oval. Stones cut in this fashion have rows of facets that are generally diamond shaped and may (or may not) be symmetrical around the stone. They placed to provide weight not light. This design is also found in many pear shaped stones with highly domed, somewhat random, pavillions.
The pavillion facets (bottom) are cut into a general hemispherical shape. The bottom facets are nearly parallel with the table guaranteeing tremendous light loss. The center of the stone has what is known as a "fish-eye", no light return, while the outside edge of the oval may look sparkly. The middle 40 -50% of the stone is a window.
This design is quite common in mass produced, native cut stones. The rounded pavillion maximizes the stones weight even though it produces very poor light return. Since these stones are usually sold by the carat, the max weight will return more money from the unwary buyer.