Making cob from coastal Texas black gumbo clay?

I've tried searching for this but nothing came back. Has anyone tried making cob from Texas black gumbo clay? It seems to turn to asphalt when dry without doing anything to it so I would think it would make great cob. I'm trying to get things together for a rocket mass heater and would like to know if anyone else has experience with this type clay. It's very sticky, you almost can't get it off a shovel if it's wet....

David

Is this the black muck you find in places like oyster beds? Lots of organic matter in it and often it has gone anaerobic and stinks of sulfur?

Well it's black muck but this is more sediment from the San Bernard River. I think it does have a lot of organic matter in it if you can figure out how to get it released. It's also hard as a rock when dry, especially with some roots running through it.

David Eakin wrote:Well it's black muck but this is more sediment from the San Bernard River. I think it does have a lot of organic matter in it if you can figure out how to get it released. It's also hard as a rock when dry, especially with some roots running through it.

Best way to get rid of organic matter is to burn it. Have you tried making a test brick of it and firing it? It may lighten up considerably once all the organic matter is burnt up. Without the fetid organic matter in it, it may make for much better starting material for a batch of cob.

Haven't done a test brick but I am planning it. As hard as this soil is to work with I was hoping it would at least be good for something...

David Eakin : have you seen the Clay for RMH Thread at the Rocket stoves forums? And we are asking everyone this month to find the permies tool box above your
original post and Click on MY PROFILE to add your general location and growing season number if you know it ! for the Crafts, big AL