Like East Africa’s most widely respected gem, tsavorite garnet, chrome tourmaline has a rich, bright, clean green that has no real counterpart among other tourmalines. Indeed, novices are apt to mistake fine chrome tourmaline for fine tsavorite.
They shouldn’t feel bad, however. So do the experts. “The finest quality chrome tourmalines are only distinguishable from tsavorite with the aid of a gemological instrument such as a refractometer,” says one gem expert. (The refractive index of chrome tourmaline is usually 1.62-1.64 while that of tsavorite is 1.74.)
Very recently, some superb stones have tempted comparison to very fine Colombian emerald. These gems have a lovely bluish-green cast not seen in tsavorite.
More commonly, very fine chrome tourmalines lean more toward the yellow than the blue end of the spectrum. But whether yellowish or bluish, their chromium content is what gives them their bright, sharp, vivid color. Collectors can test for chromium content with a Chelsea filter. Under the filter, chrome-laden stones will show flashes of red or orangy red.
The Chelsea test is the main way dealers confirm the East African origin of green tourmaline. Far more abundant green tourmalines from Brazil, Afghanistan, Maine and California are colored primarily by iron. So when these stones are subjected to a Chelsea filter test, their color remains green.
Even without a filter, “chromes” have a unique visual appeal. At their best, they boast an almost corrosively brilliant color. Of course, this uniqueness is reflected in their prices which generally are three times that of a normal green tourmaline, although not approaching the pinnacle of Paraiba tourmaline.
Caught In The Middle
Although chrome tourmaline is scarcer than tsavorite, it is not plagued by the size problem of that garnet. Chrome tourmaline occurs fairly frequently in sizes up to ten carats while tsavorite is extremely hard to fine in sizes over two carats. For this reason, top-grade tsavorites around two carats easily command ten times what kindred-caliber chrome tourmalines around two carats will cost.
Yet demand for chrome tourmaline is probably less than one-hundredth that for tsavorite. Why? “Jewelers don’t think of chrome tourmaline as a bargain compared to tsavorite,” says a New Jersey importer. “They think of it as very expensive tourmaline.”
This is not to say that chrome tourmaline doesn’t have its followers. Virtually unknown before 1970, this tourmaline has now become the color standard for deep green in this gem. As said before, it has something to do with East Africa and the special aura that surrounds its gems, especially the green ones.
A word of caution is necessary here, though. Many chrome tourmalines do not possess the fine green we are describing. According to dealers, only one of the two Tanzanian mines that produce this gem can be counted on for a fairly steady but thin flow of fine stones. It is called the Landanai mine and its stones are usually free of the brownish overtones that mar the tourmalines from its more productive sister mine.
Brownishness isn’t the only problem with chrome tourmaline. Often stones will be so saturate with green that they appear blackish or over dark. Unless price is your prime consideration, we advise steering clear of either brownish or blackish stones. “If you must compromise,” a dealer says, “go with lighter, livelier stones.”