GemCad Ray Traces for RI = 1.63  
Random Model  Cosine Model  ISO Model 
Barion Square Cushion 2
GemCad Derived Rendering by Bob Keller July 2000 

Angles for R.I. = 1.63  105 facets + 16 facets on girdle = 121 
4fold, mirrorimage symmetry  96 index 
L/W = 1.000 T/W = 0.523 T/L = 0.523 P/W = 0.526 C/W = 0.175  H/W = (P+C)/W+0.02 = 0.721 P/H = 0.729 C/H = 0.243 
Vol./W^3 = 0.319  Brightness at 0 degrees tilt for RI = 1.63
COS = 79.6 ISO = 87.1 
Pavilion  

1  41.50  0309152127333945
5157636975818793  Cut to meet at temporary culet 
g2  90.00  0321274551697593  Meet 1 establish size, girdle outline 
g3  90.00  0123254749717395  Meet 1,g2 
4  65.00  0321274551697593  Meet 1,g2 
5  65.76  0123254749717395  Meet g2,g3,4 
6  40.00  0618304254667890  Meet 1,4,5  permanent culet 
Crown  
A  49.00  0321274551697593  Establish upper girdle line 
B  49.00  0123254749717395  Meet g2,g3,A 
C  39.00  0321274551697593  Leave across face width of A = .0908W 
D  39.00  0123254749717395  Meet ABC 
E  29.00  0321274551697593  Leave across face width of C = .0767W 
F  29.00  0123254749717395  Meet CDE 
G  19.00  0321274551697593  Leave across face width of E = .0681W 
H  19.00  0123254749717395  Meet EFG 
T  0.00  Table  Leave face across width of G = .0630W 
Basil Watermeyer was the inventor of the barion concept, and the first barions were square shaped stones with step cut crowns and barion pavilions faceted from diamond. The barion concept and style has since been extended to colored stones and virtually all of the standard shapes as well as baroques. This square cushion's step cut crown combined with a straight forward barion pavilion produces the "light fountain effect" Basil Watermeyer attributes to his original barions.
The width of facets in "step cut" courses are not determined or controlled by a meet point, as they are when cutting meet point style, and sometimes step cut or mixed cut designs are referred to as "irreproducible" for that reason. Establishing the width of the first course on a step cut crown can be particularly difficult to judge by eye alone. However, you can do better than just eyeball estimating the width of step cut courses by using a little math and a pair of calipers to give yourself a visual reference and a reality check.
The width of the stone is W, and this design has a table width equal to .523W. That leaves a total crown planview width of .477W for the facets surrounding the table. .477W divided by 8 equal width steps (4 on each side of the table) equals a crown planview width of .0596W for each step.
Unfortunately, the planview width of the crown facets is not something you can put a pair of calipers directly up against to measure, except for the table at an elevation angle of zero degrees, the only case where the planview width and the across face width are equal. All the other crown facets have a zaxis component (height), so their across face widths form the hypotenuses of right triangles with the planview width legs adjacent to the facet elevation angle. The heights form perpendicular legs opposite the facet elevation angle.
Knowing the planview width (.0596W) of the step facets, the across face (hypotenuse) width for each tier can be calculated as .0596W / cos(elevation angle).
So if your stone were 12mm wide, the planview width of each step would be .0596 x 12mm = .7152mm, yielding:
First tier  across face width (A and B)  =  .7152mm / cos(49 degrees)  =  1.09mm 
Second tier  across face width (C and D)  =  .7152mm / cos(39 degrees)  =  .920mm 
Third tier  across face width (E and F)  =  .7152mm / cos(29 degrees)  =  .817mm 
Fourth tier  across face width (G and H)  =  .7152mm / cos(19 degrees)  =  .756mm 
A tip for cutting this and other designs with step cut crowns is to take your time after the transfer and establish the most perfectly level girdle that you can as a base upon which to build the step cut courses. If your girdle is level and you are careful not to overcut, step cut courses are straightforward to cut. If your girdle is not level going in, you may wind up cheating yourself blind trying to match up the meets on the suceeding step cut courses.