Hiddenite is a very rare variety of the species spodumene, named after the geologist W.E. Hidden who discovered the stone in 1879, in North Carolina (USA). It is emerald green in colour, with chromium acting as the colouring agent. A light green spodumene also occurs, coloured by iron not chromium; deposits of this material are more abundant. The light green material may also be referred to as hiddenite in the gem trade, although gemmologists and collectors would classify it as simply 'green spodumene'.
As with other varieties of spodumene, the colour can fade, so protection from sunlight and strong artificial light is recommended.
Source locations for hiddenite include: Brazil, China, Madagascar and USA (North Carolina).
Irradiation is used to improve the colour of light green stones, the resulting colour is not stable. It will fade on exposure to strong light.