A high temperature furnace adapted to expand mineral
ores such as vermiculite, perlite and the like. The fur
nace preferably includes an upright, vertically oriented
frame adapted to support an elongated furnace tube into
which mineral ore is delivered for expansion. Raw ore
may be routed through a preheating system including a
plurality of vertically spaced-apart, inclined baf?es
removably disposed within a preheating enclosure se
cured to the furnace. A preheater bypass system is in
cluded to facilitate use of the furnace with vermiculite.
Flame control and mineral waste control are preferably
effectuated with a ?ame guide adapted to be variably
positioned intermediate a lower blast nozzle and a fur
nace tube heat input ori?ce. A plurality of thermal
expansion couplings and supports are utilized to com
pensate for thermal expansion.