Manufacture of stone wool.
Stone wool is a furnace product of molten stone, at a temperature of about 1600°C, through which is blown a stream of air or steam. More high tech production techniques are based on spinning molten rock (lava) on high speed spinning wheels. (compare with candy floss) The final product is a mass of fine intertwined fibres with a typical diameter of 6 to 10 micrometres. Mineral wool may contain a binder and an oil to reduce dusting and making it water repellent (hydrophobic).
The fibres themselves are excellent conductors of heat, but they package air so well, that when pressed into rolls and sheets, rockwool makes for an excellent and reliable insulator. Batts, sheets and roll made of rockwool are a poor conductor of heat and sound. Fire resistive properties for mineral wools is given here in descending order:
No conventional building materials, including mineral wool are immune to the effects of fire of sufficient duration or intensity. However, each of the aforementioned three wools make common components in passive fire protection systems, such as in spray fireproofing, stud cavities in drywall assemblies required to have a fire-resistance rating, packing materials in firestops and more.
Mineral wools are unattractive to rodents but will provide a structure for bacterial growth if allowed to become wet.
Other uses are in resin bonded panels, growth medium in hydroponics, filler in compounds for gaskets, brake pads, in plastics in the automotive industry and as a filtering medium.
( from: Wikipedia )