Mount Ida Heart by Bob Keller

Mount Ida Heart - designed by Bob Keller ©1998
Angles for R.I. = 1.5480 facets + 15 facets on girdle = 95
1-fold, mirror-image symmetry96 index
L/W = 1.006 T/W = 0.600 T/L = 0.597 P/W = 0.575 C/W = 0.176H/W = (P+C)/W+0.02 = 0.772 P/H = 0.745 C/H = 0.229
Vol./W^3 = 0.277Brightness at 0 degrees tilt for R.I. = 1.54
COS = 35.7 ISO = 40.8

Pavilion
P146.00°03-09-15-21-27-33-39-42-45-48-51-54-57-63-69-75-81-87-93Cut to permanent center point
G190.00°48Establish size, lower girdle line
G290.00°38-58G2-G8 match corresponding P1 facets
G390.00°32-64 
G490.00°23-73 
G590.00°18-78 
G690.00°14-82 
G790.00°11-85 
G890.00°07-89 
B270.00°38-58B2-B8 match G2-G8, make level lower girdle line
B370.00°32-64 
B470.00°23-73 
B570.00°18-78 
B670.00°14-82 
B770.00°11-85 
B870.00°07-89 
B152.00°48Meet G1.P1.P1.B2.G2
Crown
A153.00°48Steps A1-A8 match G1-G8, make level upper girdle line
A253.00°38-58 
A353.00°32-64 
A453.00°23-73 
A553.00°18-78 
A653.00°14-82 
A753.00°11-85 
A853.00°07-89 
B142.00°48Steps B1-B8 match A1-A8
B242.00°38-58 
B342.00°v32-64 
B442.00°23-73 
B542.00°18-78 
B642.00°14-82 
B742.00°11-85 
B842.00°07-89 
C124.00°48.00Steps C1-C8 match B1-B8
C224.00°38-58 
C324.00°32-64 
C424.00°23-73 
C524.00°18-78 
C624.00°14-82 
C724.00°11-85 
C824.00°07-89 
T0.00°TableCut level table

Download PDF format printer friendly cutting instructions: [ Download Icon Mount Ida Heart Printer Icon ]

Download the GemCad format design file: [ Download Icon mount_ida_heart.gem ]

Mount Ida Heart Cutting Notes

I had several design goals and criteria for this design. Shown at left is the prototype stone, which measures 17mm from flat to point, cut from a water clear crystal of Mount Ida's finest. Because hearts have just one fold of symmetry, they are inevitably more involved and time consuming to cut than higher order symmetry designs such as rounds, triangles, rectangles, etc.

I wanted to cut a heart but wasn't really looking forward to making all the elevation angle changes required by many heart designs. I considered free-forming a completely step cut design, working from the girdle in. I noticed that hearts are pretty close to 1:1 in length to width, which suggested using a round pavilion, mated to the heart shaped girdle by barion facets. This is easy to do with freeforms, and produces stones of normal depth when the length to width is close to 1:1.

My original thinking was to cut the heart completely 'on the lap' but I couldn't resist playing with it in GemCad first to at least roughly determine the indexing required for a heart shaped outline. Once in GemCad, I realized that the pavilion and girdle could be completely described in a meetpoint sequence that would generate a reproducible heart shaped outline. After the 46° P1 pavilion mains are cut to centerpoint, the 90° G1-G8 facets are cut to meet with the mains and create a 'preform'.

The preforming meets between the pavilion mains and G2-G8 are cut away by the corresponding 70° B2-B8 facets, which create a level girdle line as they are cut in. Note that B2-B8 meet G2-G8 and not with the corresponding P1 facets. Looks like there are a lot of steps but there are only 4 angles required to cut the pavilion and girdle - 46° on the P1 mains, 90° on the G1-G8 girdle facets, 70° on the B2-B8 barion break facets, and 52° on the B1 "vee" facet. I've broken down the steps on the instructions to reflect that there are changes of elevation between index pairs, even though they are part of a course which is cut at the same angle. Index and elevation changes are quick and easy on my Graves Mark IV, angle changes are more demanding and time consuming.

The crown is formed by a simple 3 tier course of step cuts, the A1-A8 tier forms the upper girdle line. Each tier is cut at a constant angle with different elevations for the index pairs within each tier. Including the table, there are only 4 angles required to cut the crown - 53° on the first tier, 42° on the second tier, 24° on the third tier, and 0° on the table. I've learned that time spent establishing a dead level girdle after transferring is time and frustration saved on cutting and cheating each succeeding tier of a step cut crown.

Once I had this design rendered in GemCad, I had to play with the raytrace, of course. By doing so, the angles have evolved into something quite a bit different from those I'd have used if I had just cut 'on the lap'. The raytrace on this design indicated a (relatively) bright, vee-shaped heart appearing inside the table. I say relatively, because in the course of optimizing the contrast and shape of that effect, I used 46° mains on the pavilion and high crown angles, which are generally going the wrong way for absolute brightness.

However, I wasn't overly concerned with making the prototype stone too dark. Besides being cut from clear quartz, it's also fairly large, and when it comes to returning photons, there's just no substitute for aperture... ;) This stone exhibits much better dispersion than most of my quartz stones, which I attribute to the generally higher angles employed.

I was motivated more than usual as I wanted to get this stone finished over the holidays before Tucson '99 so I'd have something new to show off during the Show. I cut this stone in less than 2 weeks, which I'm pretty sure is a record for me. It proved to be as easy to cut as I'd hoped and the results are gratifying. That vee-shaped heart is really in there! I will probably have the prototype wirewrapped as a necklace pendant for a Valentine's Day gift.

While I seldom cut the same design more than once, I plan to follow on with another of these cut from some pale amethyst, or perhaps some rose quartz if I can find some that's not too sleepy. This design should also be suitable for glass or inexpensive rough marketed as 'synthetic' quartz, much of which is not artificially grown quartz, but glass with a lower RI and hardness. Takes a hell of a polish with cerium oxide though, and red quartz is tough to find...

If you cut a Mount Ida Heart of your own, be sure and let me know what you've cut and how you made out.


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Bob Keller