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To Stack or Unstack Mains?

  • Writer: BESPOKEGEMS.UK
    BESPOKEGEMS.UK
  • Jun 23
  • 2 min read

Among gemstone designers – and cutters – there has been a long and ongoing debate concerning the relative merits of gems in which the crown main facets are aligned with the pavilion main facets (stacked mains) versus those in which the crown main facets are placed between the pavilion main facets (unstacked mains). Some argue that ‘unstacked mains’ designs produce more sparkle (scintillation) but in terms of some designs, including the Standard Round Brilliant, there appears to be little difference in performance. Furthermore, in this writer’s opinion the traditional stacked version of the SRB gives a somewhat crisper face up appearance than the unstacked version.

The Standard Round Brilliant with stacked mains, left, and with unstacked mains, right. Renditions from Gem Cut Studio.
The Standard Round Brilliant with stacked mains, left, and with unstacked mains, right. Renditions from Gem Cut Studio.

However, for some designs there is no question that an unstacked version produces a better visual effect than the stacked version of the same design. Here is an example involving an 80 index design requested by a family member fascinated by all things to do with pentagrams. The design is called Binary Star (see a 2022 post) and involves the use of similarly proportioned main facets on both the crown and the pavilion, with those on the former being truncated by the table. Apart from incorporating the asked for pentagrams in physical form, my objective was to produce a design in which a five-pointed star was also an obvious visual feature. Before cutting the design in a natural material I decided to test cut both a stacked version in synthetic spinel with a RI of 1.72 and an unstacked version in synthetic corundum with a RI of 1.76. With suitable minor adjustments in GCS both produced similar renditions of both versions of the design with renditions of the unstacked version suggesting that this, rather than the stacked version, would produce the visual effect I was looking for.

Binary Star with stacked mains on the left and with unstacked mains, Binary Star (Decoupled) on the right.
Binary Star with stacked mains on the left and with unstacked mains, Binary Star (Decoupled) on the right.

Computer renditions of designs, particularly those from GCS, are a great aid but nothing beats physical observation of cut stones. Here, left, is the stacked version in spinel, and right the unstacked version in corundum.

Binary Star with stacked mains on the left and with unstacked mains, Binary Star (Decoupled) on the right.
Binary Star with stacked mains on the left and with unstacked mains, Binary Star (Decoupled) on the right.

In the case of this design, there is no doubt that the unstacked version produces a much better visual effect.

 
 
 

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