A combustion tube comprises a generally cylindrical body with an outwardly extending annular tube stop spaced from one end of the combustion tube for engaging a combustion tube mounting assembly and fixing the tube in a precise position. Near the opposite end of the tube is an enlarged opening for receiving an upper seal assembly of a combustion furnace with the outer annular shoulder of the upper end of the tube having a rolled edge to facilitate the insertion of the tube through the seal in the upper seal assembly of the furnace. The combustion tube is made of quartz glass to withstand the temperatures encountered in the furnace. The combustion tube is specifically designed and adapted to be precisely positioned in an induction furnace with an easy tube removal system for the furnace.