Turquoise contains copper which is the source of its blue or greenish blue color. Many minerals, such as variscite, naturally resemble turquoise. Other minerals can be dyed to imitate it. Turquoise imparts peace upon the wearer.
Tanzanite (a variety of the mineral zoisite) was discovered in 1967 in northern Tanzania, which remains the world’s only known source. Its velvety, purplish blue color sets it apart from all other gems. Tanzanite is said to give its wearers balance.
Source: GIA Gem Encyclopedia