More to the point, the bare stone would look ravaged to him ... But the direct application of plaster can damage precious color traces. Now, 3-D laser scanning can produce a copy without contact ...

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 ...

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