A mineral fragment is placed in a cavity on a charcoal block, and a horizontal flame is sent towards the fragment on the charcoal using a blowpipe. Depending on the mineral, a different reaction takes place. Certain metals have a characteristic color when flamed, and if the mineral being tested contains such a metal, the charcoal turns that color behind the fragment.
Some minerals form a metal bead after being flamed, others give off fumes, and a few volatilize.