But... WHAT is a "twinning wisp"??
Very hard to spot is what they are!! Actually they are a remnant of the twinning process in the diamond crystal. So as the crystal is forming, it can twist on an axis (sort of like a rubics cube). The resulting crystal continues to grow but now the the "halves" on either side of the twinning plane are growing in different directions. The following example is a quartz crystal (not a diamond) but it shows more clearly how the crystal would have been straight had it not twinned.
Here's an actual twinned diamond crystal that we in the biz call a "macle". Rough of this shape gets used to make trillions, hearts and other shapes that can take advantage of an oddly shaped and often shallow rough.
SOOO to finally answer your question...a twinning wisp is a group of inclusions that formed when the crystal twinned and so exist in only one plane (the twinning plane). It may be made up of needles or crystals or what-have-you but the important thing is that they all exist together in the same 2-Dimensional plane within the stone. Often times they are found in a central location and tend to radiate outwards toward the edges of the stone, like a wispy cloud. Here's a pic:
These twinning wisps are toward the side of the finished stone but if you were to turn the stone and look at them through the girdle, they would all be in the same plane.
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