Silicates—including quartz, mica, olivine, and precious minerals such ... trace elements can produce other colors, allowing beryl to form semiprecious stones such as aquamarine.

As is the case with many stones, an amethyst's value is determined by several factors, including color, clarity, carat, and cut. Here is how these factors play into the price of this precious gem.

semi precious gemstones ... As with other colored gemstones, color is one of the most important factors determining the price ...