Colored stones are rarely vivid. The most common color is yellow with a red tint. The most valuable is pink. Siberian topazes lose some color in sunlight. The rough stones should not be scratch tested because of the danger of cleavage. Care must be taken during polishing and setting for the same reason. They are not resistant to sulphuric acid.
Deposits are associated with pegmatites or secondary placers.
Topazes weighing several kilos are known. In 1965 a blue topaz of nearly 100kg was said to be found in the Ukraine .The Smithsonian Institution of Washington has cut topazes of several thousand carats.
Colored stones are usually emerald or scissor cut, and colorless ones are brilliant cut. Topazes with disordered inclusions are cut en cabochon.
The quartz variety citrine and yellow heat-treated amethyst are falsely called “gold topaz” or “Madeira topaz”, so real topaz is sometimes referred as “precious topaz”

*Info by Walter Schumann “Gemstones of the World”