• Table

    Large flat facet centered on the crown of a polished diamond.

  • Table Size

    Measure of the table width expressed as a percentage of the diameter. Table size is a proportion important to the balance between brilliance and dispersion.

  • Tapered Baguette Cut

    Diamond cut or shaped into a triangle with one corner cut off, and rows or steps of elongated facets running parallel to the girdle on both the crown and the pavilion. It is a modified version of a standard baguette cut.

  • Tone

    Degree or depth of colour in terms of lightness or darkness. The tone of a coloured diamond can range from very pale to very dark; it is the degree to which the colour of a diamond approaches white on the pale end, and black on the dark end.

  • Toughness

    Measure of brittleness, or resistance to fracture and breaking. Diamond has very good durability, but due to its directional hardness diamonds have certain planes of weakness along which they can split or break. Toughness and hardness together determine the durability of diamond.

  • Transparency

    Degree to which a diamond transmits light, directly relevant to the cloudiness or haziness of the actual diamond material, and the quality of the crystal. Click here to learn more about transparency and the DCLA Transparency Grading System.

  • Treated Diamond

    Diamonds that are artificially enhanced, to improve either colour or clarity. These treatments fundamentally alter the diamond from its natural state, and therefore need to be fully disclosed. Click here to learn more about treated diamonds.

  • Trigon

    Triangular shaped natural, with very fine triangular concentric lines. Trigons, when present, are a definitive indicator of natural diamonds.

  • Trilliant

    Diamond cut or shaped into a triangle, sometimes with curved sides.

  • Twinning Line

    Type of diamond inclusion that appears as a line or ribbon of pinpoints, tiny feathers, clouds, and crystals. Twinning lines are created where two rough diamonds have grown together in the earth under extreme heat and pressure.