The world we live in has given birth to more than 4,000 minerals. These are found in various combinations in the three forms of rock we learned about in school long ago: igneous, sedimentary and metamorphic. Of all these minerals, only 100 or so are common. They are made up mostly of the eight most common elements in the earth's crust. Each is distinguished by a particular chemical composition that combines these elements, and a specific crystal structure that does so in a certain atomic pattern.(A very few have no orderly internal structure, such as opal, and the organic gemstones, like amber.)

A gemstone is defined by its beauty, durability and rarity. All of these aspects are relative, but only beauty is completely subjective. Even so, whatever we call its beauty always results from the gemstone's appearance, and therefore its interaction with the energy of light. Optics is the science that studies this interaction.

Each of the Four C's (color, clarity, quality of cut, and carat weight) can be related to one or more of the three value characteristics just mentioned.  Diamond is the only gemstone made of just one element (carbon), and, as such, has the potential to crystallize with the greatest purity, resulting in the highest clarity, as well as the most transparency, and the greatest hardness.

The 4 C's apply to colored stones differently than to diamonds. Colored stones' quality is judged, first, by color (as simple as that sounds, it is not), and second, its "life," that is, liveliness, or what is called brilliance in a diamond. Life is created by the way a stone is cut to take advantage of how much it bends the light that enters it. It is also influenced by clarity, because more inclusions impede the passage of light through the material.

But color is more important. Each species of stone speaks in its own "language" of color, and some species speak in such completely different "dialects" as to seem unrelated (corundum, for example, includes both ruby and sapphire, colored by different trace elements). The words used to describe their appearance have historically been drawn from comparisons with the natural world (“pigeon blood” ruby or “cornflower blue” sapphire). They require an interpreter, so to speak, for the unfamiliar buyer to make the right decision. I serve you in this capacity, by showing you different qualities of the gemstone species you're considering.

Because colored stone markets are smaller than that for diamond, they are less well-organized and understood, but they are growing larger with the rise of the middle class in other parts of the world, where colored stones have always been valued more highly than we do, in places closer to where most of them are mined. 

This desire, and improved technological methods, are why a myriad of gemstone treatments to enhance apparent quality have appeared faster and faster. Some have been around for thousands of years and others are more recent. Some are accepted (heat treatment of almost all aquamarine and tanzanite, for example). Others are not (the plague of lead glass-treated ruby sold to U.S. troops in Afghanistan without disclosure, for example). A few are only done with the intent to deceive (adding green dye to jade or emerald).

Nothing greens greener, it has been said, than emerald. For the ideal color of any species, we never see anything like it anywhere else in the world - nothing "reds redder" than ruby or "blues bluer" than sapphire. But these are matters of experience., because there are many shades of green, red and blue, and the human memory is notoriously short for them. If you seek deep insight into quality and value as you acquire a fine colored gemstone, please let me lend you my connoisseur's eye.