Arsenic is a semi-metallic element. Arsenic and its compounds are known to be toxic.

Arsenic has two forms. The grey metallic version has a density of 5.73g/cm3 and the yellow form that has a density of 1.97g/cm3.
Discovery

While arsenic has been in use since ancient times, in applications such as the hardening of bronze, its discovery has been attributed to Albertus Magnus in 1250AD. He isolated arsenic when he heated soap and orpiment (arsenic trisulphide, As2S3).
Occurrence

Although arsenic can be found in elemental form, it is most commonly found in minerals such as Mispickel (arsenopyrite, FeSAs) which is found in France, Germany, Italy, Romania, Siberia and North America.

Arsenic is also found in other minerals such as:

· Realgar As4S4

· Orpiment As2S3

· Arsenolite As2O3

· Loellingite FeAs2