AboutDr Thomas Bell Expertise I can answer questions regarding surface earth processes and the chemical transformations that sediments and rocks undergo with burial. I can also answer questions regarding deep time, the evolution of the elements, and the last 4.5 billion years of earth history. I specialize in metallic ore forming processes, the major geologic time periods when they were produced and what they tell us about the evolution of our planet. Learn more about my professional interests at Stratamodel.com.
Experience I am a professional consulting geologist with a background in the petroleum, mining, environmental, and geotechnical industries with over 25 years of experience.
Education/Credentials Ph.D., Geology, University of California at Berkeley, 1984
M.A., Geology, University of California at Berkeley, 1980
B.S., Geology, San Jose State University, 1978
Question I am looking for some rock that can withstand heat. I am building an outdoor fireplace and looking to rock to use in place of firebricks.
Answer Carmen,
The problem you are trying to solve is an old one. Long before recorded history a few solutions arose based on natural materials. Ordinarily, one would now use fire brick to solve this problem. This brick has a very high concentration of alumina rich clay. Material scientists have been improving on them as our technological demands for heat resistant materials have grown. You are looking for a natural material that has little expansion and contraction when heated or cooled. You need a material that has a melting point far higher than the highest temperature of your fire.
On past camping trips we have speculated about which rocks around our campfire would explode if heated enough. The general consensus was that wet porous rocks could be heated fast enough to 'pop' as water heated to steam blowing the rocks apart. Another popular camping pastime is to melt a wine or beer bottle. Getting a campfire hot enough to burn an aluminum beer can is also instructive.
So, what can you learn about lining your fireplace from a bunch of fun loving geologists on a camping trip? Go for an igneous rock of some sort like granite. Or line the interior of your fireplace with shale, a rock composed of aluminum rich clay minerals. Be sure that whatever rock you use is dry and not porous enough to absorb much water.
