Allochromatic Color
A large number of minerals occur in a wide range of colors caused by impurities or light absorbing defects in the atomic crystal structure. Impurities are traces of elements (Cr, Mn, Fe, Ni, Cu...) that are not present in the pure mineral compound. Therefore allochromatic colors are variable and unpredictable mineral properties, eg. Tourmaline can be black, green or pink.
Verdelite - Green variation of Tourmaline (Cr-traces)
Cyclosilicates
Na(Li,Al,Mg,Mn,Fe)3Al6(BO3)3[Si6O18](OH)4
Minas Gerais, Brazil
Size: 8 cm
Schorl - Black variation of Tourmaline (Fe-traces)
Cyclosilicates
Na(Li,Al,Mg,Mn,Fe)3Al6(BO3)3[Si6O18](OH)4
Minas Gerais, Brazil & United Kingdom
Size: (Left) 4cm / (Middle) 9 cm / (Right) 3 cm
Rubellite - Pink variation of Tourmaline (Mn-traces)
Cyclosilicates
Na(Li,Al,Mg,Mn,Fe)3Al6(BO3)3[Si6O18](OH)4
Minas Gerais, Brazil
Size: 18x13 cm
Indicolite - Blue variation of Tourmaline (Li-traces)
Cyclosilicates
Na(Li,Al,Mg,Mn,Fe)3Al6(BO3)3[Si6O18](OH)4
Minnesota, USA
Size: 7 cm
Zoned blue-yellow Fluorite
Halides
CaF2
Illinois, USA
Size: 10 cm
Zoned green-purple Fluorite
Halides
CaF2
Illinois, USA
Size: 9 cm
Purple Fluorite
Halides
CaF2
Kansas, USA
Size: 12cm
Green Fluorite
Halides
CaF2
Hebei, China
Size: 8x7 cm
Yellow Fluorite
CaF2
Hebei, China
Size: 21cm
Ruby (red variety of Corundum) in Zoisite
Oxides
Al2O3
Burma
Size: (Top) 26cm