While topaz is quite hard, its toughness and resistance to blows is considered poor because of its perfect directional cleavage. Treated gems may be even more vulnerable to cleaving. Ultrasonic cleaners and steamers should be avoided. A soft, damp cloth remains the best way to clean topaz and topaz jewellery.
Colour is the principal feature of topaz with pink to orange to reddish orange combinations being among the most collectible. Size of the gemstone is also an important attribute, even in irradiated material where huge museum-quality gems are occasionally available.
Heating: In some cases, yellow or brown topaz may be changed to pink or red colours
Irradiation / followed by heating: this treatment begins with induced irradiation causing colourless topaz to turn brown or brownish green. A heat treatment follows, turning the material blue. In rare cases, some material may retain residual radioactivity which has generally disappeared before it reaches the end consumer
Topaz occurs in a broad range of colors
Yellow and golden colors are most known for topaz
Topaz sometimes includes a soft blending of pinkish orange to reddish orange colours, which the gem trade has called “imperial topaz”
Natural blue topaz exists but is generally pale
Topaz from most sources is reasonably clean and eye-clean stones are both desirable and possible
Pink and red topaz are normally only available in small stones and a slightly higher degree of inclusions are tolerated. These inclusions are usually liquid inclusions
Occasionally trapped minerals such as rutile can be found in topaz.
In very rare cases, tiny ribbon like hollow tubes, forming in parallel fashion, cause cat’s eye effect
Topaz has perfect cleavage in one direction, so carvings are rare. When they do occur, especially by known artists, they are soon collected.
What is Mystic Topaz? Information provided by Dutch Gemological Laboratory
What is Mystic Topaz?
‘Mystic Topaz’ is ”real” Topaz that is coated to add color. Much of the Topaz that is found in nature is in fact colorless, or ‘white’. To add color, Topaz can be coated with an ultra thin layer (film), which is similar to the coatings used on camera lenses.
Such coatings can add a particular color to the treated stones, or, In the case of ‘Mystic Topaz’, the coating creates interference effects, displaying a rainbow effect of various colors. This effect may give the Topaz an artificial appearance (see photos), which sometimes causes confusion about the nature of the material.
The quality of the created rainbow effect in Mystic Topaz (is it really pleasing to the eye or not) and the visibility (or absence) of inclusions could determine the difference in quality between the individual stones.
Potential problems with Mystic Topaz
Coatings can be scratched or damaged easily. It should therefore be handled with the same care as pearls for example. The coating is sensitive to chemicals and therefore one needs to remove the jewelry when doing household activities that include bleach for example or before going into a swimming pool.
Although Topaz is a hard substance, it can be cleaved rather easily and perfectly in one particular direction. Therefore, boiling in water or the use of an ultrasonic cleaner are not recommended when cleaning pieces of jewelry set with Topaz.
The particular rough in the second photo comes from the Elahera district, Sri Lanka, a locality where large chunks of colorless topaz are found.