Applicable to:

• Brilliant
• Rounded Fancies / Marquise, Oval, Pear

All facets of the Brilliant, Marquise, Oval and Pear cuts may be divided into layers: main crown facets, upper facets, star facets, main pavilion facets, lower girdle facets (halves)(figure 1).

Figure 1. Facets of a diamond.

Facets of each layer are sorted by azimuth, then the slope and azimuth of each facet is estimated. The azimuth is measured in the range from 0 to 360 degrees. The slope is measured in the range from 0 to 90 degrees. Table facet has zero slope (figure 2).

Figure 2. Measurements of slope angle and azimuth angle for the main facet.

The slope angle of the crown main facet is the Crown angle in the Helium report.

Figure 3. Crown angle and pavilion angle.

Comprehensive list of the Helium report parameters:

• Position normalization
• Diameters, Width & Length
• Main diameters
• Ratio (L/W) & Girdle Ratio
• Table
• Culet
• Total height
• Crown height
• Pavilion depth
• Upper and lower girdle facets’ heights
• Crown height at girdle minima
• Pavilion depth at girdle minima
• Depth and length girdle facets
• Girdle thickness
• Girdle types for cushion as red, yellow, green and blue
• Corner angle width and Corner angle length
• Facets' slope and azimuth angle
• Facets' slope and azimuth angle for rounded fancies (obsolete)
• Azimuths deviation from ideal
• MIC & Girdle to MIC
• Girdle-Table offset (by table axis),
  Girdle-Culet offset (by table axis),
  Table-Culet offset (by table axis)
• Crown painting and Pavilion painting
• Girdle type (obsolete)
• Trapezium parameters
• Extra Facet / Natural
• Twist
• Statistical values

Measurements are used in different systems and tools:

• Lower girdle facets or halves
• OctoNus spread & AGS spread