Judge an old mine cushion through its outline, facets, spread and condition. Watch how the central and outer facets exchange light as the stone moves.
Start with the outline
Many are softly square, but elongated and irregular examples are common. Compare the corners, shoulders and sides. Hand-cut asymmetry can add character; a distracting bulge or flat side is harder to explain away.
Watch the broad facets
A high crown, small table, deep pavilion, short lower-half facets and open culet often create broad flashes and clear contrast. A still image freezes the pattern. Video shows whether the bright and dark areas trade places.
Compare dimensions with weight
Carat measures weight. The millimetre dimensions describe the visible size. Record length, width and depth, then consider the ratio, corners and face-up coverage on the hand.
Check condition before choosing a setting
Inspect the girdle for thin sections, chips, naturals, abrasions and old repairs. A setter should map vulnerable areas before designing the seats.
Read colour and clarity through the cut
Large open facets can make body colour and some inclusions easier to see. Ask whether an inclusion affects transparency or durability. Discuss the position and visibility of the features as well as the grade.
Use normal light
Check diffused daylight for brightness, small direct lights for fire and ordinary room light for daily appearance. Include the lighting in which you expect to wear the diamond most often.
GIA describes the typical high crown, small table, deep pavilion and open culet in its cushion-cut history. For a current stone, compare its report with on-hand video and direct inspection.