Step 4: Gem Grading

Lesson 3

The Role of Nature in Gem Evaluation

Even a cursory review of color, clarity, and carat and their functions reveals that Nature bestows these qualities on gems. We have little control over them.

Color?

What is gemstone color but a visual demonstration of contamination? Trace amounts of visiting chemicals create an exciting array of gem colors. Take the mineral corundum, for example. Add sufficient chromium and the great, grand ruby emerges. Then, add iron oxide and luscious sapphire arises. That same iron oxide added to the mineral beryl produces aquamarine. But add that same chromium to beryl and you get a shimmering emerald. These awesome transformations occur in nature.

In the laboratory, that arena of human manipulation, we can exert our will over gem color. However, we simply mimic the natural phenomenon.

Clarity?

For how many eons did the heat and pressure of geological forces rudely forge gem crystals out of trapped chemicals? These forces left telltale markers as undeniable evidence of this natural process. Next, consider what other forces — primitive mining operations, accidents, and stone papers — introduced additional “demerits” to gemstones. Humans have very…