|Angles worked out on GemCad by Jack Rowland|
|Angles for R.I. = 1.54||29 facets + 8 facets on girdle = 37|
|2-fold, mirror image symmetry||32 index|
|L/W = 1.250 T/W = 0.739 T/L = 0.591||P/W = 0.535 C/W = 0.184|
|H/W = (P+C)/W+0.02 = 0.739||P/H = 0.724 C/H = 0.249|
|Vol./W^3 = 0.455|
|g1||90.00||32-16||Cut to form girdle side|
|g2||90.00||08-24||Cut to square with g1|
|b1||52.00||32-16||Leave about 1/3 for crown|
|c1||42.00||32-16||Cut by eye about 1/2 way|
|c2||42.00||08-24||Cut to meet with c1|
|b3||52.00||05-11-21-27||Cut to b1-b2-c1-c2 meet|
|B1||42.00||32-16||Leave some girdle|
|M1||32.00||32-16||Cut to B1-B2 meet|
|M2||32.00||08-24||Cut to B1-B2 meet|
|S1||22.00||32-16||Cut until M1 is smaller than B1|
|S2||22.00||08-24||Cut to meet with S1|
|T||0.00||Table||Cut by eye until S1-S2 smaller than M|
The emerald, or Trap Cut is a very old cut. It's name is derived from the dutch word for stair which is trap- the same place the name "trap door" comes from. Many folks that cut their teeth using meetpoint faceting shy away from this very versatile cut. Without modification this design will cut gems with a length to width ratio of 1.2 to 1 to more than 2 to 1. This allows very good use of certain crystals such as tourmaline who's shape is a perfect preform for this cut. A note of caution. Trap cuts are deep and deepen the color of the stone. If too dark material is used the stone will end up too dark. It is best used on light to medium colored rough.
To cut this stone rough out the girdle outline to make best use of the rough. Don't go for any given length to width, just don't make it square or nearly so. You want the girdle to go all the way around the stone where the final girdle will end up. This should be around 1/3 of the way from the dop to the tip.
Now cut break facets on the long side at 52 degrees up to where you want the girdle to be. Level this out on the short side to end up with a level girdle outline. Next we cut the culet facets at 42 degrees until the depth of the Break and the Culet facets are about the same. This is not super critical, just get it close by eye. Level the Culet facets all the way around. Cut the corner breaks at 52 degrees just to where the Break and Culet facets meet. Now level the girdle at the same index setting.
Be sure to polish the long culet facets with the lap turning toward the tip. A knife edge will chip (always) if you polish the other way.
The Crown is just as simple, and again, not critical. Just cut the breaks to level the girdle, then the mains to the break corner meets, then cut the star facets and table by eye. If you have trouble getting things to level up it is because you are not using consistent pressure at the end of the cut. This causes the facet on one side to be cut more deeply than on the other side. Try using no pressure at all at the end of the cut & let the machine weight finish up until cutting stops by itself. Also note that you may need to cheat the index setting for some of the long facets to polish.
Index of Gem Designs
Perfect Transfer Index
Table of Contents
© Bob's Rock Shop Bob Keller