Articles from 2016

In this article, we look at the relationship between the various fancy color diamonond's color grades in terms of price. We present the relative price variations between the main fancy color grades of a 1.00-carat pure yellow colored diamond (without secondary moderators) as they currently appear in our extensive database of about $350 million worth of GIA-certified fancy colored diamonds currently being offered for sale on the Internet by leading traders.

Ametrine is a bi-colored variety of quartz, composed of amethyst, with purple hues, and citrine, with yellow to orange hues. Almost all polished ametrine gems are fashioned in an emerald-cut style to emphasize the color border. We had the oppotunity to analyze some remarkable ametrine images received courtesy of L. Allen Brown, the owner of All That Glitters from Methuen, MA.

The Morogoro area in Tanzania is the source of many gemstones, and most notably spinel, ruby, sapphire and tourmaline. For many years fine quality chrome tourmaline were mined in this and other areas in Tanzania, and during past decade substantial quantities have been produced of fine quality rough tourmaline in earth tone colors, ranging from reddish orange to brown to yellow and green. These highly dichroic gems, show different colors and/or different intensities when observed from different angles, and they were the subject of our color analysis and research.

Would you believe me if I told you that the time of day that you close a deal may well affect your success in the gemstone business? It's true, and it is something I learned relatively late in life. In fact it took me more than 30 years before realizing why dealers in Bangkok insisted on showing me the sapphire lots before lunch and the ruby lots only in the afternoon.

"A gem, in order to be a gem and valuable, has to have beauty, rarity and durability." It was the first sentence uttered by my teacher, Michael O'Donoghue, when I began my formal gemological studies. Which brings me to the subject of spinel. I don't know why, but in the early days, like most gem dealers I never thought much of them. But over more than a decade, and especially after several close encounters with spinels in Mahenge, Tanzania, I have become totally enchanted by the gemstone.

Amber is not exactly a gemstone. It is a gem material derived from the petrified resin of ancient 'Umbrella Pine' trees, as well as other species. From a color perspective it is located in the white to yellow to orange-red range, although greens (enhancements) and rare blues (high blue fluorescence) can also be found. Among its many sources, the Baltic Sea region is considered to be one of the more prestigious. In this color analysis article we explore the range of colors of natural Baltic Sea ambers.

Zultanite, also known as Csarite®, is a rare color-change variety of diaspore found exclusively in Turkey. It is named for the sultan rulers who used to govern the region in the Anatolian mountains where it is sourced. When holding a zultanite gemstone in your hand, you will find it hard to describe its body color. The variety of colors produced by the gem and the distinct differences between them make it impossible for a single color description. But the GemePro™ analysis provided us with a practical solution.

Recently, with the appearance in the market of natural, rare untreated "fancy color" tanzanite gems (in colors other than blue and violet), a vivid debate has flared up amongst gemologists and traders alike. The hot-potato question is whether tanzanite can be defined as tanzanite even if they are in colors other than blue, or should they be called zoisite?

A color that is specific to tanzanite, and one which is desired especially by gem collectors, is a green-violet mixture displayed as an unusual zoning within the crystal. After fashioning and polishing, due to the facets angles, the colors merge and produce a remarkable metallic color. A 6.31-carat emerald-cut tanzanite, offered by Advanced Quality ACC, was brought to Gemewizard® for color analysis. Since its metallic color was clearly visible, we decided to analyze each color component of the gem separately, using a polarizing filter.

In Part I, we discussed the effect of a Brown or brownish second color moderator on the price of colored diamonds. In Part II herein, we shall explore the effects of Gray and grayish second color moderators on the overall appearance and value of a stone.

Some fancy colored diamonds possess a third color in their grading reports. These third colors, referred to as second color moderators, may either be Brown, brownish, Gray or grayish. Generally, the brown tint is found in diamonds with warm body colors (such as Yellow, Orange, Pink, Red, etc.), while gray is found in the cooler colors (Blue, Green, Violet).

To me the word "natural" in gems is sacred, and ideally should refer only to gemstones that were created in nature, not having undergone any process other than cutting, polishing and cleaning. But how far do we have to go with treatments in order to discard the magic word "natural"? Will a product made out of corundum powder that has been mixed with leaded glass still be called a natural ruby?

One of the trickiest gems to evaluate is an opal. This beautiful gem displays a distinctive phenomenon of colored flashes, which reflect from the stone while it is rotated. The effect is called "Play of Color," and it is a term that well explains the experience. While most gems are graded using the classical factors - color, clarity, weight, etc. - Play of Color is an additional factor that must be considered with opal. How is this done?

There is another interesting case that we may at times overlook, and that is the cut and its effect on color. Sometimes, the analyzed polished gem reflects contrasting colors from its inner facets. Mixing these reflected colors may sometimes provide a meaningless aveage color. Gemewizard's Sampler also returns the dominant colors it has identified. In essence they are the separated reflected rays, and are the colors that are key for obtaining a correct analysis.

Every year, for the past 38 years in or around February, I rediscover a new world - my own Galapagos. A word of warning - all of the inhabitants of this world are afflicted with the same disease from which I suffer. It is extremely contagious and, once contracting it, it's there for life. I'm talking about gem disease, and this hidden place is Tucson, which comes to life each year during the annual gems and minerals festival, when tens of thousands flock in for the scores of shows and exhibitions being held around the city.