trillion-cut

20:17 Dec 18, 2016 

Unfortunately I can't tell either. The individual terms seem to overlap at least to a certain extent.

18:47 Dec 16, 2016 

Thanks for the added link! Question is: What term is more common? I don't have ten diamonds at home, so I can't tell :)

If I understand it correctly, some may call it "trillion" even if it's a "Triangel" (see your link), so you may be right back where you started.

To explain what I mean:
"There are many ways to draw a triangle, and there are many ways to craft a triangle cut diamond. There are also many names the triangle shaped diamonds appear under in the marketplace: trillion, trilliant, and trillium – all of which describe a diamond cut in a shape of a triangle."
http://guide.diamondpriceguru.com/diamond-and-ring-basics/di...

Or:
"Phantasieschliff beim Diamant = Diamant-Triangelschliff. Besitzt eine dreieckige Tafel, um die sich drei parallele Reihen von treppenförmigen Facetten anschließen."
http://www.beyars.com/lexikon/lexikon_1104.html

Doesn't seem to match, does it?

18:40 Dec 16, 2016 

Wenn ich groß bin, kaufe ich mir mal so einen ;-)

18:37 Dec 16, 2016 

18:29 Dec 16, 2016 

"The term trillion or trilliant is used to describe a gemstone cut that is triangular in shape. Originally, trilliant referred to a diamond cut developed by the Asscher brothers in Amsterdam. The trilliant cut was essentially an adaptation of the brilliant cut for triangular diamonds, with straight sides and usually 43 to 50 facets.

Today the names trillion or trilliant are used for all triangular gems, regardless of the faceting pattern. Even triangular cabochons are now referred to as trillions. Though the term trilliant is used to refer to triangular diamonds, trillion has become more popular for color colored gemstones."
http://www.ajsgem.com/articles/trillion-cut-gemstones.html

"Polygone
Dreieck (Triangel, Trillant): Dreieckige Grundform in der Ausführung Brillantschliff mit Tafel, sechs viereckigen und 18 dreieckigen Facetten. Auch die Ausführung im Treppenschliff ist möglich."
https://de.wikipedia.org/wiki/Schliff_(Schmuckstein)

This may help you with the rest of your text:
http://www.juwelenmarkt.de/diamanten-4c.htm