rock sterilization...blow torch?

[RadleyMiller]

That can have catastrophic effects. If there is any moisture within the crystallization lattices in the rock's makeup, a 600F heating could cause a sudden boil-off of the liquid. The boil-off results in a rapid expansion of the liquid that may cause the rock to explode.
Ovens and/or kilns are only safe with porous materials since any trapped moisture would have avenues of escape.

If you don't believe Oddball go to a pottery place and make something. Then when you are done, get out a syringe and put an air bubble in it. Seal it up and watch it go BOOM.

Bleach or Boil, thats the only way.

 

[Bud8Fan]

That can have catastrophic effects. If there is any moisture within the crystallization lattices in the rock's makeup, a 600F heating could cause a sudden boil-off of the liquid. The boil-off results in a rapid expansion of the liquid that may cause the rock to explode.
Ovens and/or kilns are only safe with porous materials since any trapped moisture would have avenues of escape.

250 degrees is plenty hot enough to kill bacteria. I seriously doubt 250 degrees will cause a rock to explode. And if you are worried about "sudden" boil off put the rock in at the same time you turn the oven on and let it slowly heat up.

 

[fishnutham]

oddball took the words right out of my mouth..

 

[Oddball]

250 degrees is plenty hot enough to kill bacteria. I seriously doubt 250 degrees will cause a rock to explode. And if you are worried about "sudden" boil off put the rock in at the same time you turn the oven on and let it slowly heat up.

At sea level, and 1 atmosphere, water boils at 100C (212F) with a barometric pressure just under 30.0 (if memory serves). If that water is contained in a pocket (called a vug) in a stone or within a crystalline structure (called an enhydro), that water may require higher temps to boil. However, during the temp rise, pressure is being exerted within the stone from the water molecules expanding due to increased kinetic energy levels. This expansion can result in the rock exploding well before the water has reached a sufficient temperature to cause a state change of boiling into steam. Sudden boil-off occurs if a lattice cracks and the pressure changes in the trapped water that allows it to reach boiling at a lower temp. This type of fracture can be like a gun going off with rock "buck-shot" speeding out in the direction of the crack and the main mass of the rock rocketing in the opposite direction.

 

[Bud8Fan]

So only cook it at 200.

What stops said frock from blowing up when you boil it?

 

[Oddball]

Nothing. The rock will be fine with boiling PROVIDED there is no water within the rock. I'm a lapidarist. I've had rocks explode or shatter from the most minimal amount of mechanical manipulation. These warnings are put out simply because the possibility exists that a problem may arise from heating stones unless you really know the geology of the material you're working with.

Bleaching and brushing is the best method of cleaning rocks before using them in aquariums.