Muzo is the most famous of Colombia ’s emerald mines. it has produced stones of matchless beauty for more than 1000 years. The rare, fine, saturated green crystals sometimes found there are the yardstick by which all other emeralds are judged.
The colour of the finest Muzo emeralds has been described by some as “a grass green.” This is not a good description. Grasses come in a wide range of greens which tend to be greyish or brownish. The finest Muzo emeralds are noted for having a much, purer green colour. Examining your lawn, and you’ll probably agree that it doesn’t not have a top-grade emerald colour.
It’s debatable as to which are the most valuable emerald hues and tones, but gem dealers agree their saturation level should be strong and not weak or greyish, and that pure intense colours are more desirable than dull, muddy ones. In high quality emeralds, the bright areas of colour should not look greyish or brownish.
The tone (lightness or darkness of the colour) also plays a major role in the price of an emerald. For example, a medium green emerald selling for $5000 might be worth less than $100 if it were very light green. There is simply a much greater demand for medium and deep green emeralds and their supply is more limited However, emeralds should not be so dark that they look blackish. Your first impression of an emerald should be that it’s green, not black.
Opinions differ as to What tone is ideal for an emerald. According to the GIA, the most valued emeralds have a medium tone. Some dealers, however, prefer medium-dark l emeralds because their bright areas may appear more saturated in colour.
One can conclude/that top-grade emeralds range in tone from medium to medium-dark.
Judging the hue of an emerald (the position on the colour spectrum) is not any easier than judging that of a ruby. Like rubies, emeralds can also display different hues and tones simultaneously. They are a blend of two transition hues-bluish green and yellowish green. If you look at an emerald from different directions while moving it, you may be able to see these two transition hues. Keep in mind, though, that emerald colour is judged from the face-up view. The overall hue of an emerald is considered to be the average or dominant colour reflected in its bright facet areas. According to the GM Coloured Stone Course, the most desirable emerald hues are bluish green to green. As with tone, trader-Members differ a little on which hue(s) they consider best.
Some dealers for example, prefers slightly yellowish- green emeralds. They feel that a yellowish tint gives an emerald a warm feeling.
Some appraisals think that a very slightly bluish green is the most expensive hue. Because emeralds are dichroic, even slightly bluish emeralds have flashes of yellow.
For Jack Abraham, a New York gem dealer, a green green is the ideal hue. He also feels that hue is a matter of taste and goes on to say that many of the finest Muzo emeralds are slightly bluish.
Some researchers in Gemmology and mineralogy, suggest that bluish green is the best emerald hue. They explain that emeralds are cut so that “the colour seen in such a gem is largely the bluish-green prized by most connoisseurs of emeralds above the yellowish-green that would appear if the gem were cut with the table perpendicular to the c-axis.”
I. A. Mumme writes in his book The Emerald, “For those who prefer the spectroscope as a method of testing the colour of an emerald, a colour about 5000A (i.e. slightly towards the bluish-end of the green portion of the white light spectrum) would be very close an approximation to the colour of fine emerald.
Another prize colour being accepted by gem valuators today is the deep yellow green colour of Sandawana emeralds.”
When emerald colour is discussed, the country of origin may be mentioned. Some dealers say they can often tell where a stone comes from just by its colour. There’s good reason for this. The colouring agent(s) of emeralds can vary from one locality to another. The green of Colombian emeralds, for example, is caused by chromium, whereas Brazilian emeralds of good quality are generally coloured by vanadium. The colouring agent of light-coloured Brazilian emeralds is frequently iron. However, new emerald finds are making it more difficult to determine origin solely by appearance. It’s not uncommon to find Pakistani and Afghan emeralds with the same colour as high-quality Colombian emeralds.
Even though characteristic emerald colours are associated with different regions, keep in mind that there can be a wide variation of colour within each emerald mine. Don’t assume that just because an emerald is from Colombia, it’s of high quality. Neither should you assume that it’s inferior if found outside of Colombia. Many fine-quality emeralds have originated in Africa, Afghanistan, Pakistan, and Brazil. You must judge each stone on its own merits.