Furnaces; industrial furnaces; crystal growth furnaces; crystal growth furnaces used to produce sapphire boules; electric furnaces for growing crystals, namely, sapphire boules; furnaces used for growing single crystals; furnaces for growing crystals for the manufacture of sapphire boules; furnaces for industrial use, other than for experimental purposes, namely, crystal growth furnaces for use in LED backlighting, solid-state lighting, and automotive and signage applications, optical, industrial and defense applications; crystal growth furnaces for producing near-net cores, furnaces for directional solidification growth of crystal, furnaces for forming c-plane sapphire boules, furnaces for production of sapphire wafers used in LEDs; structural parts for all of the foregoing