Thallium
Discovered : by W. Crookes in 1861

Isolated in London, UK

Origin : The name is derived from the Greek ‘thallos’, meaning green shoot.

Description :

A soft, grey metal, rather like lead but it tarnishes easily. It is very toxic. Its compounds were once used in rat poisons and hair removers but are now banned.

Image :

Green shoots and reflective glass. Click here to see larger version of this image.