Aquamarine

Composition: Beryl. Beryllium Aluminium Silicate, often with sodium, lithium, and cesium
Hardness: 7.5 - 8

Metaphysical Properties: Courage, protection. Stimulates intellect and spiritual awareness.

Corresponding Chakra: Throat Chakra
Corresponding Astrological Signs: Gemini, Pisces, Aries