Pale Pink To Strong Red, Purpleish Red, Reddish Purple, Orange Red, Orange, Yellow, Yellowish To Pinkish Yellow, Yellowish Brown, Brown, Light Blue To Dark Greenish Blue, Pale Green, Colorless, Grayish
Sherry Topaz, Hyacinth Topaz, Imperial Topaz, Precious Topaz, Swiss Blue, London Blue, Mystic Topaz
refractive index, birefringence, optic character; possibly specific gravity. The refractive index of blue topaz varieties may be lower than others by as much as 0.01. Some topaz is coated, causing an inert reaction to LWUV and SWUV, different spectra and variable reactions to a CCF test.
Crystal habit is typically an orthorhombic prism, with rhombic cross-section, basal cleavage and striations along the length of the crystal (c-axis). Misnomers: slave's diamond-colorless topaz, Brazilian sapphire-blue topaz. Sherry topaz: brownish yellow to orange to yellow brown the color of sherry. Hyacinth topaz: dark orange, dark orange-red to reddish brown. Imperial topaz: top color medium reddish orange. Precious topaz: yellow and orange. Sky blue topaz: light blue irradiated topaz. Swiss blue topaz: medium blue irradiated topaz. London blue topaz: darker greenish blue irradiated topaz. Colorless and gray topaz has RI 1.609 to 1.617. Red, pink, purple, orange, yellow and brown stones: RI typically 1.629 to 1.637. Surface treated green stones: RI 1.609 to 1.617. Many times the the stones are long and thin and show pleochroic colors at the far ends of the stone. Birthstone for November