|Hard Cushion (hard_cushion.gem)|
|Angles worked out on GemCad by Jack Rowland||Copyright 1994 J.C. Rowland|
|Angles for R.I. = 1.54||57 facets + 16 facets on girdle = 73|
|4-fold, mirror-image symmetry||96 index|
|L/W = 1.000 T/W = 0.484 T/L = 0.484||P/W = 0.453 C/W = 0.149|
|H/W = (P+C)/W+0.02 = 0.623||P/H = 0.728 C/H = 0.239|
|Vol./W^3 = 0.239|
|b1||42.50||01-23-25-47-49-71-73-95||Cut to center point|
|b2||41.50||03-21-27-45-51-69-75-93||Cut to center point|
|m||41.70||02-22-26-46-50-70-74-94||Cut to girdle meets & center point|
|B1||33.00||03-21-27-45-51-69-75-93||Cut to M2-girdle meet & M1-M2-B2|
|B2||32.00||01-23-25-47-49-71-73-95||Cut to M1-girdle meet|
|S||21.00||02-22-26-46-50-70-74-94||Cut to M1-M2-B1-B2 meet|
|T||0.00||Table||Cut to M1-S & M2-S meets|
|note: Cut false temporary crown breaks at 80 degrees to give you a line to shoot for when cutting the mains. These will be cut away by B1 & B2. Cut both mains to the temporary break-girdle meets.|
The crown of this cut was inspired by many of the great old diamond cuts. This sort of crown is very versatile for an expert cutter and can be used with variation of angle to maximize yield. I coupled this with a facet doubling concept developed by Basil Watermeyer (inventor of the barion cuts) and got a design that works very well for low RI material like quartz, but even better on items like garnet and sapphire. I like the cut much better for lighter material due to the brilliance you end up with. Feel free to drop the pavilion angles a degree or two for higher RI material, but stay at least 1.5 degrees above the critical angle.
This cut is a bit more challenging than most in that you must adhere to the cutting sequence to make the meet points come in. You also must cut both Main Crown facets to exactly the same depth on the girdle. To make this easier I strongly suggest that you cut the B1 and B2 facets first at 60-80 degrees to give you a girdle line to aim for. These well be cut away later with the final angles.
Care must be taken in the polishing stage to be sure to polish b2 pavilion and the B1 and M1 crown facets with the lap moving toward the sharp corner. The corner will chip if you don't.
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© Bob's Rock Shop Bob Keller