| Spodumene, LiAl(SiO3)2, is another interesting aluminium silicate. It occurs in large quantities in South Dakota. The green, transparent variety is called hiddenite and occurs in North Carolina. The transparent, lilac or violet-coloured variety is known as kunzite it occurs in California and Madagascar and is a valuable gem-stone. Various lithium-aluminium silicates have been prepared artificially, but they do not agree in physical properties with any known lithium minerals. |