Hi Jody, welcome to Permies...
I am sorry, your question is fine, but
the answer is no. Cobb, (and its related mixes) are all based on a matrix of clay...nothing else function like that. You could use soapstone slabs carved to form a dome (I have done that) but its labor intensive, more expensive and takes different skill sets, as is working with refractory materials. I am sure you can find a potter in your area...there scrap will work just fine. You could also find a farm, or other open space and locate a vein of it (as permission) and locals...they will often help you find it. We are here to help
should you have additional questions.
Regards,
j