Here is a brief description of selenium. Selenium can be prepared with either an amorphous or crystalline structure.
Elemental selenium is relatively nontoxic and is considered to be an essential trace element.
Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Here is a brief summary of the isolation of selenium. It is not usually necessary to make selenium in the laboratory as it is commercially available. While there are several selenium ores, most selenium is made as a byproduct of copper refining. It also accumulates in the residues from sulphuric acid manufacture.