The changes taking place in tanzania makes tanzanite a very good investment stone. Iolite gemstones fancy color tanzanite color change diaspore yellow or golden beryl spinel gemstone prices an exceptional 2 21 ct demantoid type a jade from burma canary yellow tourmaline refractive index chart thai gemstones rare gems top 10 investment gems an amazing paraiba tourmaline rough and cut gemstones a gorgeous 6 ct mahenge spinel. Tanzanite also competes with lab created sapphires that are lower in price.