Topaz

Topaz

Blue topaz is almost always colourless topaz that has been treated to turn blue. London blue is the deepest, inky tone; sky blue the lightest.

  • Blue topazBlue topaz
  • London blue topazLondon blue topaz

At a glance

Mineral
Topaz (aluminium silicate with fluorine)
Refractive index
1.62
Dispersion (C–F)
0.008
Specific gravity
3.53
Mohs hardness
8
Wear
Hard, but it can split along one direction (perfect cleavage): avoid hard knocks.

Topaz in Jart

The 2 looks in the studio's material library, with the values the renderer uses.

Optics of Topaz in Jart
StoneColourRIDispersion C–FAbbeSGColour depth
Blue topaz#4aa8e81.620.008773.536.9 mm
London blue topaz#3a6c9c1.620.008773.538 mm

RI refractive index (nd). Dispersion C–F nF − nC, the spread between blue and red light; many gem tables quote the B–G figure instead (diamond 0.044, here 0.025). Abbe number: lower means more fire. SG specific gravity, used for carat estimates in Design Facts. Colour depth the path through the stone after which white light takes the stone's full colour; shorter paths look paler.

How it renders

With a refractive index of 1.62, a polished topaz facet reflects 5.6% of light that meets it face-on (diamond: 17.2%). Light inside the stone that meets a facet more than 38.1° from straight on cannot leave and is reflected back in; the smaller that angle, the more light a good cut returns to the eye (diamond 24.4°, quartz 40.4°).

Its dispersion (C–F) is 0.008, 33% of diamond's, which sets how much fire, the flashes of colour, a render shows under small, bright lights.

Both presets share topaz's optics; London blue reaches its colour over a slightly longer path but in a darker tone, so it reads deeper in small stones.

  • 1 mm
  • 3 mm
  • 6 mm
  • 10 mm
Blue topaz: the colour of white light after 1, 3, 6 and 10 mm of stone. It takes the full preset colour at 6.9 mm.
  • 1 mm
  • 3 mm
  • 6 mm
  • 10 mm
London blue topaz: the colour of white light after 1, 3, 6 and 10 mm of stone. It takes the full preset colour at 8 mm.

All gemstones · Metals · Stone and metal pairings · Finishes

Render topaz on your own design.

Open a 3DM, STL or GLB file, or a sample ring, choose the stone and the metal, and render it photoreal in your browser. No account needed.

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