Trilliant cut

[Cave Keeper]

Being a neophyte, I only came across the trilliant cut last week.

What is this "triangular" cut for?

Mathmatically, isn''t this shape the most wasteful of all shapes? Conversely, why should the ''round'' brilliant cut be considered the most wasteful, material-wise, when it contains the most volume for a given perimeter?

 

[valeria101]

'cause the "given perimeter" an dvolume has a specific shape too! So the least "wasteful" shape is the largest effective prism that follows the shape of the rough. By now there is specialized software that does the fitting (Garry's domanin). You will likely find it interesting to follow the story of how diamon cuts evolved... any implicit rules are all for you to guess

For a trilliant, the start of the story is the shape of the rough, and you can look at some samples HERE and HERE, for example. Most likely, the respective trilliant came from a macle.

Also, you would need to keep in mind that more than one diamond may come from a sigle piece of rough - since, it makes more sense to get a couple of smaller diamonds than the largest feasible of any pebble (literally, shown HERE).

The worst part of such "optimization" is that one has to take into account that the internal characteristics of the material need consideration - I bet it is not only the flawless rough that is cut. So fitting the shape of the stone with the shape of the rough is not the whole story - by all means.

 

[Michael_E]

Cave Keeper,
Wastefulness depends totally on the shape of the rough stone that you start cutting from. If the rough is triangular, then the least waste comes from cutting the finished stone to as close to the perimeter of the rough as possible. My avatar is a triangular tourmaline that started as a poorly cut oval that was a very ugly mix of green and pink. In order to get the best color and cut out the green I elected to cut that stone into a sort of "squashed" cushion triangle. In this case I wanted to have as much waste as it took to remove the green.
Basically the final shape of a gem is determined by a great many factors which include: rough shape including pits and crevices, internal inclusions and their location and direction, color zoning and location of best color, dichroism and the direction of the best color, cleavage directions and of course the desired final shape. A round brilliant is considered most wasteful not due to mathmatical considerations, but because most rough gems are not round.