A tier is a set of facets cut at the same angle, at several index positions around the stone. A faceting design lists its tiers in cutting order.
In more detail
Round brilliants have tiers such as the pavilion mains, lower halves, crown mains, stars and upper halves. The T73 has 3 crown tiers and 2 pavilion tiers.
How we measure it
Our tier table lists the angle, indices and cutting order of every tier. Our cut pages take the main crown and pavilion angles from the tiers that the design gives.
Related terms
- Facet: A facet is one flat, polished face of a cut gemstone. Its angle and its direction around the stone decide where it sends light.
- Index gear: An index gear is the toothed wheel on a faceting machine that sets each facet's direction around the stone. Each index is one tooth of the gear.
- Tier table: A tier table lists the angle, index positions and cutting order of every tier in a faceting design. Ours comes as a .csv file that opens in any spreadsheet.
- Cutting order: Cutting order is the sequence in which a faceter cuts the tiers of a design. Each new tier is cut to meet the tiers before it.
- GemCad .asc: GemCad is Robert Strickland's faceting design program for Windows, and .asc is its text design format. An .asc file gives the gear, the refractive index and every facet's angle and index.