On 23 September 1885, Auer von Welsbach received a patent on his development of the gas mantle, which he called Auerlicht, using a chemical mixture of 60% magnesium oxide, 20% lanthanum oxide and 20% yttrium oxide, which he called Actinophor. To produce a mantle, guncotton is impregnated with a mixture of Actinophor and then heated, the cotton eventually burns away, leaving a solid (albeit fragile) ash, which glows brightly when heated. These original mantles gave off a green-tinted light and were not very successful, and his first company formed to sell them failed in 1889.
In 1890 he introduced a new form of the mantle based on a mixture of 99% thorium dioxide and 1% cerium(IV) oxide, which he developed in collaboration with his colleague Ludwig Haitinger.  These proved both more robust and having a much "whiter" light. Another company founded to produce the newer design was formed in 1891, working with fellow student from the university Ignaz Kreidl, and the device quickly spread throughout Europe.
In the United States this technique was adopted by The Coleman Company and became their logo for the company.  In the 1980s it was reported that Thorium's radio-daughters (Decay products)
could be volatilized and released into the air upon incandescence of the mantle.  
A lawsuit (Wagner v. Coleman) was brought against Coleman. The company changed its formulation to use non-radioactive materials, which apparently cost less and last longer.