North by Northwest
by Tom Herbst
North by Northwest is a very simple design.
It displays the best properties of both a classic "sparkly" stone and
a more geometric reflector. It works well in medium index material such
as tourmaline and beryl.
The name comes from the resemblance of the crown and pavilion facets
to a compass "rose," the direction indicator on old-styled maps. The
pavilion points North, and
points Northwest, hence the cinematic name.
North by Northwest is a straightforward design suitable for all skill
levels. BOG-optimized for ISO (94%) and tilt in Tourmaline. For beryl,
tangent ratio the pavilion from 43.2° to 44.2° and the crown
from 32.2° to 40°.
Pictured below is a matched pair (more or less) of 6 mm, 1
carat stones cut in flawless, pale, green-blue tourmaline
(left) and synthetic emerald (right).
GemCAD and GemRay output for North by Northwest appear below. The GemCAD file,
BOG-optimized for tourmaline, is available