Easy way to determine the "type" or composition of used bricks found on Craigslist?

I picked up a stack of 147 hearth bricks in hopes to use for a RMH, but I wonder is there is a way to know if they are appropriate for the burn tunnel and riser? I don't wish to rebuild soon after first build if the bricks break down early due to being a bad material for the high heat. I can snap some photos if they are needed, the weather is warming up a bit the next couple days.

Thanks
Bobby

The easiest way to get an idea of what you've got is to post a photo along with the measurements and weight of one of the bricks. Then you'll get some helpful feedback from those of us "in the know"

Check out "Masonry Tools" by Walter Skocylas over in the Stone Work forum. As a mason he may be able to answer your question. I'd link you there but I don't know how to yet.

Ok

This one weighs about 51 oz

Most are just over 7 1/2in by just under 3 1/2in by just over 2 1/4in

Thanks
Bobby

Those are modern common bricks, not suitable for exposure to the extreme heat and thermal shock of the combustion core. They will be fine for building other parts of the system, though.

Firebricks are commonly 4 1/2" x 9" x 2 1/2" thick, though other thicknesses are available. They are notably heavy, generally weighing around 7 or 8 pounds.
If bricks of these dimensions are notably light, and soft and easily scratched, they are probably insulating firebrick, not suitable for feed tube and burn tunnel but highly suited to heat riser or backup insulating around the core.

Ok, bummer. Thanks for the info.. Freebie and on the way somewhere one night, so no big loss. Will use somewhere outside the burn tunnel.

Bobby

There were quite a few of these on the property we bought. They are 9 something by 4 something by 2 something and this one weighs 8lb 2oz (snow wet)

This a firebrick possibility?

Hadn't googled the name yet. Apparently, it's a local Ohio company paving brick. Couldn't find a list of ingredients for them.

There were quite a few of these on the property we bought. They are 9 something by 4 something by 2 something and this one weighs 8lb 2oz (snow wet)

This a firebrick possibility?

the old bricks that are chalky will do a half decent job for a rocket stove. they are not the best but can work. the softer and "chalkier" the better. when broken in half they are usually orange-ish in color inside.