天然宝石通常远比人工合成的宝石有价值，所以能够正确鉴别它们是一项高超的技能。

Sometimes what you don’t see is as important as what you do. “Negative space” is the explanation to this curious statement.

For more than a century, the Four Peaks mine in Maricopa County, Arizona, has produced gem-quality amethyst from crystal-lined or crystal-filled cavities and fractures in a brecciated quartzite host rock.