Yellow and Golden Colored Gemstones Gemstone Crystal System Density Hardness Refractive index Treatments Agate microcrystalline 2.66 6.5-7.0 1.544-1.553 dying Amber amorphous 1.08 2.0-2.5 1.54 heating, oiling, reconstitution Beryl hexagonal 2.72 7.5-8.9 1.577-1.583 heat, radiation, fracture filling, oiling Chalcedony microcrystalline 2.66 7 1.544-1.553 dying Chrysoberyl orthorhombic 3.72 8.5 1.746-1.755 heat, radiation Citrine hexagonal 2.66 7.0 1.544-1.553 heat Diamond cubic 3.52 10 2.417 radiation, drilling, fracture filling Jadeite microcystalline 3.34 6.5-7.0 1.660-1.680 dying Opal amorphous 2.15 5.0-6.5 1.450 fracture filling Sapphire hexagonal 4.00 9 1.762-1.770 heat, fracture filling Smoky Quartz hexagonal 2.66 7.0 1.544-1.553 none Spinel cubic 3.60 8 1.718 none Tiger-eye microcrystalline 2.64-2.71 7.0 1.540-1.550 none Topaz orthorhombic 3.53 8.0 1.619-1.627 blue is irradiated Tourmaline trigonal 3.06 7.0-7.5 1.624-1.644 heat Zircon tetragonal 4.00 6.50 1.810-1.815 heat