The most valuable gem variety of crystalline quartz, amethyst ranges in color from pale lilac to deep reddish purple. The official birthstone for those born in February, amethyst is said to guard against drunkenness.
One of several gem-quality varieties of beryl, aquamarine is sought for its breathtaking sea-blue colors and its wonderful transparency and clarity. The official birthstone for those born in March, aquamarine is believed to impart foresight, courage, and happiness.
Sometimes mistaken for jade, aventurine is a compact variety of translucent to opaque quartz. Small inclusions of shiny minerals give this stone a sparkling effect, called aventurescence. (Mica inclusions give a silvery sheen. Hematite, a reddish or grayish sparkle.) Typically green, aventurine can also be peach, brown, or blue.