Alfacite ore

Edward Fisher covered in alfacite ore.

Alfacite was a type of yellowish magnetic ore which was found in abundance on planet Alfa 177.

In late 2266, the ore was accidentally introduced into the transporter system of the USS Enterprise and caused the transporter to divide lifeforms and materials, including Captain James T. Kirk, into two objects which were visually identical, but intrinsically different. Lieutenant Commander Spock later referred to this incident as the Alfacite Energy Phenomenon. (TOS episode: "The Enemy Within"; TOS short story: "Ni Var")