Dan Woloz : Bare with me a minute , we are going to use the best brick we can get to surround the Combustion Core,
Feed tube, Burn tunnel, and Heat riser
We surround that with insulation everywhere ! Outside of the well placed insulation we can use any kinda rock,
cob, brick, urbanite !
All this is a part reason for the dry stacking that we do to make sure we have the best materials by category, in each place ! There will always be a place for
Nearly any material you drag to your work site !
It is kinda late in the season to dig clay, or glean good brick from a clean fill dump, But, your
local excavation contractor knows were every local spot where
''Clean fill'' or ''spoil '' has been dumped for the last 30 years, (s)he will know where there is an old closed dump that you may be able to pick over.
You will need to call the work office and tell a secretary that you want to talk to the boss about having clean fill dumped on your property, this gets you a cell
phone number and a chance to talk to the boss, now I am Not advocating out and out lying to anyone, but you can certainly tell the Excavation Contractor that
you have a type of Brick that you want to match -true! and that you want to finish this
project but the size of the project can grow and may expand to other sights
And you would love to hook up with someone who might be able to help you match old brick and you really are into re-cycling !
Noting ventured, nothing gained ! For the Good of the Craft ! Big AL
Sorry, you really didn't get an answer to your specific question, because they have been labeled 2nd or 3rd class they do not get used much except on the
perimeter ofvthe well insulated core ! A. L. 
