Example image of eyePlorer eyePlorer map for 'Gemstone': Jewellery Mineral Amber Jet (lignite) Lapis lazuli Organic chemistry Rock (geology) Lustre (mineralogy) Engraved gem Hardstone carving Peter Carl Fabergé Ancient Greek Diamond Emerald Ruby Sapphire Mohs scale of mineral hardness Transparency and translucency Archaeology Art history Hardstone Gemology Technical terminology Empirical formula Aluminium Carbon Crystal system Cubic crystal system Monoclinic crystal system Trigonal crystal system Crystal habit Corundum Aquamarine Beryl Cleavage (crystal) Dispersion (optics) Fracture Refractive index Relative density Birefringence Pleochroism Absorption spectrum Luminescence Inclusion (mineral) Gemological Institute of America Mnemonic Optical phenomenon Star stone Opal Pearl